diff --git a/src/myfasthtml/assets/core/profiler.css b/src/myfasthtml/assets/core/profiler.css
index 7c120f6..7e8f397 100644
--- a/src/myfasthtml/assets/core/profiler.css
+++ b/src/myfasthtml/assets/core/profiler.css
@@ -162,6 +162,169 @@
     color: color-mix(in oklab, var(--color-base-content) 45%, transparent);
 }
 
+/* ------------------------------------------------------------------
+   Detail panel — right side
+   ------------------------------------------------------------------ */
+.mf-profiler-detail {
+    display: flex;
+    flex-direction: column;
+    width: 100%;
+    height: 100%;
+    overflow: hidden;
+}
+
+.mf-profiler-detail-header {
+    display: flex;
+    align-items: center;
+    gap: 8px;
+    padding: 5px 10px;
+    background: var(--color-base-200);
+    border-bottom: 1px solid var(--color-border);
+    flex-shrink: 0;
+}
+
+.mf-profiler-detail-title {
+    flex: 1;
+    font-family: var(--font-sans);
+    font-size: var(--text-sm);
+    font-weight: 500;
+    white-space: nowrap;
+    overflow: hidden;
+    text-overflow: ellipsis;
+}
+
+.mf-profiler-detail-cmd {
+    font-family: var(--font-sans);
+}
+
+.mf-profiler-detail-duration {
+    font-family: var(--font-mono);
+    font-size: var(--text-xs);
+}
+
+.mf-profiler-view-toggle {
+    display: flex;
+    gap: 2px;
+    flex-shrink: 0;
+}
+
+.mf-profiler-view-btn-active {
+    color: var(--color-primary) !important;
+    background: color-mix(in oklab, var(--color-primary) 12%, transparent) !important;
+}
+
+.mf-profiler-detail-body {
+    flex: 1;
+    overflow-y: auto;
+    padding: 10px;
+    display: flex;
+    flex-direction: column;
+    gap: 8px;
+}
+
+/* ------------------------------------------------------------------
+   Span tree — inside a Properties group card
+   ------------------------------------------------------------------ */
+.mf-profiler-span-tree-content {
+    display: flex;
+    flex-direction: column;
+}
+
+.mf-profiler-span-row {
+    display: flex;
+    align-items: center;
+    padding: 4px 10px;
+    border-bottom: 1px solid color-mix(in oklab, var(--color-border) 50%, transparent);
+}
+
+.mf-profiler-span-row:last-child {
+    border-bottom: none;
+}
+
+.mf-profiler-span-row:hover {
+    background: var(--color-base-200);
+}
+
+.mf-profiler-span-indent {
+    flex-shrink: 0;
+    width: 14px;
+    align-self: stretch;
+    border-left: 1px solid color-mix(in oklab, var(--color-border) 60%, transparent);
+}
+
+.mf-profiler-span-body {
+    flex: 1;
+    display: flex;
+    align-items: center;
+    gap: 8px;
+    padding-left: 6px;
+    min-width: 0;
+}
+
+.mf-profiler-span-name {
+    min-width: 120px;
+    font-family: var(--font-sans);
+    font-size: var(--text-xs);
+    white-space: nowrap;
+    flex-shrink: 0;
+}
+
+.mf-profiler-span-name-root {
+    font-weight: 600;
+}
+
+.mf-profiler-span-bar-bg {
+    flex: 1;
+    height: 5px;
+    background: color-mix(in oklab, var(--color-border) 80%, transparent);
+    border-radius: 3px;
+    overflow: hidden;
+    min-width: 0;
+}
+
+.mf-profiler-span-bar {
+    height: 100%;
+    border-radius: 3px;
+    background: var(--color-primary);
+}
+
+.mf-profiler-span-bar.mf-profiler-medium {
+    background: var(--color-warning);
+}
+
+.mf-profiler-span-bar.mf-profiler-slow {
+    background: var(--color-error);
+}
+
+.mf-profiler-span-ms {
+    font-family: var(--font-mono);
+    font-size: var(--text-xs);
+    color: color-mix(in oklab, var(--color-base-content) 55%, transparent);
+    min-width: 60px;
+    text-align: right;
+    flex-shrink: 0;
+}
+
+.mf-profiler-span-ms.mf-profiler-medium {
+    color: var(--color-warning);
+}
+
+.mf-profiler-span-ms.mf-profiler-slow {
+    color: var(--color-error);
+}
+
+.mf-profiler-cumulative-badge {
+    font-family: var(--font-mono);
+    font-size: 10px;
+    padding: 1px 5px;
+    border-radius: 3px;
+    background: color-mix(in oklab, var(--color-primary) 10%, transparent);
+    border: 1px solid color-mix(in oklab, var(--color-primary) 30%, transparent);
+    color: var(--color-primary);
+    flex-shrink: 0;
+    white-space: nowrap;
+}
+
 /* ------------------------------------------------------------------
    Empty state
    ------------------------------------------------------------------ */
diff --git a/src/myfasthtml/controls/Panel.py b/src/myfasthtml/controls/Panel.py
index 7b5d414..8223f1b 100644
--- a/src/myfasthtml/controls/Panel.py
+++ b/src/myfasthtml/controls/Panel.py
@@ -232,7 +232,7 @@ class Panel(MultipleInstance):
           hide_icon,
           Div(content, id=self._ids.content(side)),
           cls=panel_cls,
-          style=f"width: {self._state.left_width}px;",
+          style=f"width: {self._state.right_width}px;",
           id=self._ids.panel(side)
         )
   
diff --git a/src/myfasthtml/controls/Profiler.py b/src/myfasthtml/controls/Profiler.py
index cab237e..cfb44a5 100644
--- a/src/myfasthtml/controls/Profiler.py
+++ b/src/myfasthtml/controls/Profiler.py
@@ -5,18 +5,113 @@ from fasthtml.components import Div, Span
 from myfasthtml.controls.BaseCommands import BaseCommands
 from myfasthtml.controls.IconsHelper import IconsHelper
 from myfasthtml.controls.Panel import Panel, PanelConf
+from myfasthtml.controls.Properties import Properties, PropertiesConf
 from myfasthtml.controls.helpers import mk
 from myfasthtml.core.commands import Command
 from myfasthtml.core.constants import PROFILER_MAX_TRACES, MediaActions
 from myfasthtml.core.instances import SingleInstance
-from myfasthtml.core.profiler import profiler
-from myfasthtml.icons.fluent import arrow_clockwise20_regular
+from myfasthtml.core.profiler import CumulativeSpan, ProfilingSpan, ProfilingTrace, profiler
+from myfasthtml.icons.fluent import (
+  arrow_clockwise20_regular,
+  data_pie24_regular,
+  text_bullet_list_tree20_filled,
+)
 
 logger = logging.getLogger("Profiler")
 
 
+# ---------------------------------------------------------------------------
+# Span tree renderer — module-level, passed via PropertiesConf.types
+# ---------------------------------------------------------------------------
+
+def _mk_span_rows(span, depth: int, total_ms: float) -> list:
+  """Recursively build span rows for the tree view.
+
+  Args:
+      span: A ProfilingSpan or CumulativeSpan to render.
+      depth: Current nesting depth (controls indentation).
+      total_ms: Reference duration used to compute bar widths.
+
+  Returns:
+      List of FT elements, one per span row (depth-first order).
+  """
+  rows = []
+  indent = [Div(cls="mf-profiler-span-indent") for _ in range(depth)]
+
+  if isinstance(span, CumulativeSpan):
+    pct = (span.total_ms / total_ms * 100) if total_ms > 0 else 0
+    duration_cls = _span_duration_cls(span.total_ms)
+    badge = Span(
+      f"×{span.count} · min {span.min_ms:.2f} · avg {span.avg_ms:.2f} · max {span.max_ms:.2f} ms",
+      cls="mf-profiler-cumulative-badge",
+    )
+    row = Div(
+      *indent,
+      Div(
+        Span(span.name, cls="mf-profiler-span-name"),
+        Div(Div(style=f"width:{pct:.1f}%"), cls="mf-profiler-span-bar-bg"),
+        Span(f"{span.total_ms:.1f} ms", cls=f"mf-profiler-span-ms {duration_cls}"),
+        badge,
+        cls="mf-profiler-span-body",
+      ),
+      cls="mf-profiler-span-row",
+    )
+    rows.append(row)
+
+  else:
+    pct = (span.duration_ms / total_ms * 100) if total_ms > 0 else 0
+    duration_cls = _span_duration_cls(span.duration_ms)
+    name_cls = "mf-profiler-span-name mf-profiler-span-name-root" if depth == 0 else "mf-profiler-span-name"
+    row = Div(
+      *indent,
+      Div(
+        Span(span.name, cls=name_cls),
+        Div(Div(cls=f"mf-profiler-span-bar {duration_cls}", style=f"width:{pct:.1f}%"), cls="mf-profiler-span-bar-bg"),
+        Span(f"{span.duration_ms:.1f} ms", cls=f"mf-profiler-span-ms {duration_cls}"),
+        cls="mf-profiler-span-body",
+      ),
+      cls="mf-profiler-span-row",
+    )
+    rows.append(row)
+    for child in span.children:
+      rows.extend(_mk_span_rows(child, depth + 1, total_ms))
+
+  return rows
+
+
+def _span_duration_cls(duration_ms: float) -> str:
+  """Return the CSS modifier class for a span duration."""
+  if duration_ms < 20:
+    return "mf-profiler-fast"
+  if duration_ms < 100:
+    return "mf-profiler-medium"
+  return "mf-profiler-slow"
+
+
+def _span_tree_renderer(span: ProfilingSpan, trace: ProfilingTrace):
+  """Renderer for ProfilingSpan values in a PropertiesConf.types mapping.
+
+  Args:
+      span: The root span to render as a tree.
+      trace: The parent trace, used to compute proportional bar widths.
+
+  Returns:
+      A FT element containing the full span tree.
+  """
+  rows = _mk_span_rows(span, 0, trace.total_duration_ms)
+  return Div(*rows, cls="mf-profiler-span-tree-content")
+
+
 class Commands(BaseCommands):
   
+  def toggle_detail_view(self):
+    return Command(
+      "ProfilerToggleDetailView",
+      "Switch between tree and pie view",
+      self._owner,
+      self._owner.handle_toggle_detail_view,
+    ).htmx(target=f"#{self._id}")
+
   def toggle_enable(self):
     return Command(
       "ProfilerToggleEnable",
@@ -67,7 +162,9 @@ class Profiler(SingleInstance):
   def __init__(self, parent, _id=None):
     super().__init__(parent, _id=_id)
     self._panel = Panel(self, conf=PanelConf(show_right_title=False, show_display_right=False))
+    self._panel.set_side_visible("right", True)
     self._selected_id: str | None = None
+    self._detail_view: str = "tree"
     self.commands = Commands(self)
     logger.debug(f"Profiler created with id={self._id}")
   
@@ -92,8 +189,14 @@ class Profiler(SingleInstance):
     self._selected_id = trace_id
     return self
   
+  def handle_toggle_detail_view(self):
+    """Toggle detail panel between tree and pie view."""
+    self._detail_view = "pie" if self._detail_view == "tree" else "tree"
+    logger.debug(f"Profiler detail view set to {self._detail_view}")
+    return self
+
   def handle_refresh(self):
-    """Select a trace row and re-render to show it highlighted."""
+    """Refresh the trace list without changing selection."""
     return self
   
   # ------------------------------------------------------------------
@@ -149,7 +252,7 @@ class Profiler(SingleInstance):
       return Div("No traces recorded.", cls="mf-profiler-empty")
     
     rows = []
-    for trace in traces:
+    for trace in reversed(traces):
       ts = trace.timestamp.strftime("%H:%M:%S.") + f"{trace.timestamp.microsecond // 1000:03d}"
       duration_cls = self._duration_cls(trace.total_duration_ms)
       row_cls = "mf-profiler-row mf-profiler-row-selected" if trace.trace_id == self._selected_id else "mf-profiler-row"
@@ -183,14 +286,116 @@ class Profiler(SingleInstance):
   def _mk_detail_placeholder(self):
     """Placeholder shown in the right panel before a trace is selected."""
     return Div("Select a trace to view details.", cls="mf-profiler-empty")
+
+  def _mk_detail_header(self, trace: "ProfilingTrace"):
+    """Build the detail panel header with title and tree/pie toggle.
+
+    Args:
+        trace: The selected trace.
+
+    Returns:
+        A FT element for the detail header.
+    """
+    duration_cls = self._duration_cls(trace.total_duration_ms)
+    title = Div(
+      Span(trace.command_name, cls="mf-profiler-detail-cmd"),
+      Span(f" — {trace.total_duration_ms:.1f} ms", cls=f"mf-profiler-detail-duration {duration_cls}"),
+      cls="mf-profiler-detail-title",
+    )
+    tree_cls = "mf-profiler-view-btn mf-profiler-view-btn-active" if self._detail_view == "tree" else "mf-profiler-view-btn"
+    pie_cls = "mf-profiler-view-btn mf-profiler-view-btn-active" if self._detail_view == "pie" else "mf-profiler-view-btn"
+    toggle = Div(
+      mk.icon(text_bullet_list_tree20_filled, command=self.commands.toggle_detail_view(), tooltip="Span tree", cls=tree_cls),
+      mk.icon(data_pie24_regular, command=self.commands.toggle_detail_view(), tooltip="Pie chart (coming soon)", cls=pie_cls),
+      cls="mf-profiler-view-toggle",
+    )
+    return Div(title, toggle, cls="mf-profiler-detail-header")
+
+  def _mk_detail_body(self, trace: "ProfilingTrace"):
+    """Build the scrollable detail body: metadata, kwargs and span breakdown.
+
+    Args:
+        trace: The selected trace.
+
+    Returns:
+        A FT element for the detail body.
+    """
+    from types import SimpleNamespace
+
+    meta_props = Properties(
+      self,
+      conf=PropertiesConf(
+        obj=trace,
+        groups={"Metadata": {
+          "command": "command_name",
+          "description": "command_description",
+          "duration_ms": "total_duration_ms",
+          "timestamp": "timestamp",
+        }},
+      ),
+      _id="-detail-meta",
+    )
+
+    kwargs_obj = SimpleNamespace(**trace.kwargs) if trace.kwargs else SimpleNamespace()
+    kwargs_props = Properties(
+      self,
+      obj=kwargs_obj,
+      groups={"kwargs": {"*": ""}},
+      _id="-detail-kwargs",
+    )
+
+    span_props = None
+    if trace.root_span is not None:
+      span_props = Properties(
+        self,
+        conf=PropertiesConf(
+          obj=trace,
+          groups={"Span breakdown": {"root_span": "root_span"}},
+          types={ProfilingSpan: _span_tree_renderer},
+        ),
+        _id="-detail-spans",
+      )
+
+    if self._detail_view == "pie":
+      pie_placeholder = Div("Pie chart — coming soon.", cls="mf-profiler-empty")
+      return Div(meta_props, kwargs_props, pie_placeholder, cls="mf-profiler-detail-body")
+
+    return Div(meta_props, kwargs_props, span_props, cls="mf-profiler-detail-body")
+
+  def _mk_detail_panel(self, trace: "ProfilingTrace"):
+    """Build the full detail panel for a selected trace.
+
+    Args:
+        trace: The selected trace.
+
+    Returns:
+        A FT element for the detail panel.
+    """
+    return Div(
+      self._mk_detail_header(trace),
+      self._mk_detail_body(trace),
+      cls="mf-profiler-detail",
+    )
   
   # ------------------------------------------------------------------
   # Render
   # ------------------------------------------------------------------
   
   def render(self):
+    selected_trace = None
+    if self._selected_id is not None:
+      selected_trace = next(
+        (t for t in profiler.traces if t.trace_id == self._selected_id), None
+      )
+
+    right_panel = (
+      self._mk_detail_panel(selected_trace)
+      if selected_trace is not None
+      else self._mk_detail_placeholder()
+    )
+
     self._panel.set_main(self._mk_trace_list())
-    self._panel.set_right(self._mk_detail_placeholder())
+    self._panel.set_right(right_panel)
     return Div(
       self._mk_toolbar(),
       self._panel,
diff --git a/src/myfasthtml/controls/Properties.py b/src/myfasthtml/controls/Properties.py
index e78de5b..ebc751f 100644
--- a/src/myfasthtml/controls/Properties.py
+++ b/src/myfasthtml/controls/Properties.py
@@ -1,21 +1,46 @@
+from dataclasses import dataclass, field
+from typing import Any, Optional
+
 from fasthtml.components import Div
 from myutils.ProxyObject import ProxyObject
 
 from myfasthtml.core.instances import MultipleInstance
 
 
+@dataclass
+class PropertiesConf:
+  """Declarative configuration for the Properties control.
+
+  Attributes:
+      obj: The Python object whose attributes are displayed.
+      groups: Mapping of group name to ProxyObject spec.
+      types: Mapping of Python type to renderer callable.
+          Each renderer has the signature ``(value, obj) -> FT``.
+  """
+
+  obj: Any = None
+  groups: Optional[dict] = None
+  types: Optional[dict] = field(default=None)
+
+
 class Properties(MultipleInstance):
-  def __init__(self, parent, obj=None, groups: dict = None, _id=None):
+  def __init__(self, parent, obj=None, groups: dict = None, conf: PropertiesConf = None, _id=None):
     super().__init__(parent, _id=_id)
-    self.obj = obj
-    self.groups = groups
+    if conf is not None:
+      self.obj = conf.obj
+      self.groups = conf.groups
+      self._types = conf.types or {}
+    else:
+      self.obj = obj
+      self.groups = groups
+      self._types = {}
     self.properties_by_group = self._create_properties_by_group()
-  
+
   def set_obj(self, obj, groups: dict = None):
     self.obj = obj
     self.groups = groups
     self.properties_by_group = self._create_properties_by_group()
-  
+
   def _mk_group_content(self, properties: dict):
     return Div(
       *[
@@ -28,25 +53,53 @@ class Properties(MultipleInstance):
       ],
       cls="mf-properties-group-content"
     )
-  
+
   def _mk_property_value(self, value):
+    for t, renderer in self._types.items():
+      if isinstance(value, t):
+        return renderer(value, self.obj)
+
     if isinstance(value, dict):
       return self._mk_group_content(value)
-    
+
     if isinstance(value, (list, tuple)):
       return self._mk_group_content({i: item for i, item in enumerate(value)})
-    
+
     return Div(str(value),
                cls="mf-properties-value",
                title=str(value))
-  
+
+  def _render_group_content(self, proxy) -> Div:
+    """Render a group's content.
+
+    When the group contains exactly one property whose type is registered in
+    ``_types``, the type renderer replaces the entire group content (not just
+    the value cell).  This lets custom renderers (e.g. span trees) fill the
+    full card width without a key/value row wrapper.
+
+    Otherwise, the standard key/value row layout is used.
+
+    Args:
+        proxy: ProxyObject for this group.
+
+    Returns:
+        A FT element containing the group content.
+    """
+    properties = proxy.as_dict()
+    if len(properties) == 1:
+      k, v = next(iter(properties.items()))
+      for t, renderer in self._types.items():
+        if isinstance(v, t):
+          return renderer(v, self.obj)
+    return self._mk_group_content(properties)
+
   def render(self):
     return Div(
       *[
           Div(
             Div(
               Div(group_name if group_name is not None else "", cls="mf-properties-group-header"),
-              self._mk_group_content(proxy.as_dict()),
+              self._render_group_content(proxy),
               cls="mf-properties-group-container"
             ),
             cls="mf-properties-group-card"
@@ -56,12 +109,12 @@ class Properties(MultipleInstance):
       id=self._id,
       cls="mf-properties"
     )
-  
+
   def _create_properties_by_group(self):
     if self.groups is None:
       return {None: ProxyObject(self.obj, {"*": ""})}
-    
+
     return {k: ProxyObject(self.obj, v) for k, v in self.groups.items()}
-  
+
   def __ft__(self):
     return self.render()