diff --git a/src/lib/components/Preview.svelte b/src/lib/components/Preview.svelte
index 581f206..910e722 100644
--- a/src/lib/components/Preview.svelte
+++ b/src/lib/components/Preview.svelte
@@ -1,20 +1,20 @@
 <script lang="ts">
   import { parser } from "$lib/parser";
-  import { Button, Heading, P, Tooltip } from "flowbite-svelte";
+    import { hoverTargetId } from "$lib/stores";
+  import { Button, Heading, P, Textarea, Tooltip } from "flowbite-svelte";
   import { CaretDownSolid, CaretUpSolid, EditOutline } from "flowbite-svelte-icons";
 
   export let sectionClass: string = '';
-
-  export let rootIndexId: string;
+  export let isSectionStart: boolean = false;
+  export let rootId: string;
   export let depth: number = 0;
   export let allowEditing: boolean = false;
-  // TODO: Add editing functionality.
-  const isEditing: boolean = false;
 
-  const title = $parser.getIndexTitle(rootIndexId);
-  const orderedChildren = $parser.getOrderedChildIds(rootIndexId);
-  const childIndices = $parser.getChildIndexIds(rootIndexId);
-  const childZettels = $parser.getChildZettelIds(rootIndexId);
+  let isEditing: boolean = false;
+  let currentContent: string;
+
+  const title = $parser.getIndexTitle(rootId);
+  const orderedChildren = $parser.getOrderedChildIds(rootId);
 
   const getHeadingTag = (depth: number) => {
     switch (depth) {
@@ -30,41 +30,141 @@
       return "h6";
     }
   };
+
+  const handleFocus = (e: Event) => {
+    const target = e.target as HTMLElement;
+    if (target.id === rootId) {
+      $hoverTargetId = rootId;
+      e.stopPropagation();
+    }
+  };
+
+  const handleBlur = (e: Event) => {
+    const target = e.target as HTMLElement;
+    if (target.id === rootId) {
+      $hoverTargetId = '';
+      e.stopPropagation();
+    }
+  };
+
+  // TODO: Trigger rerender when editing state changes.
+  const toggleEditing = (id: string, shouldSave: boolean = true) => {
+    const editing = isEditing;
+    currentContent = $parser.getContent(id);
+
+    if (editing && shouldSave) {
+      // TODO: Save updated content.
+    }
+
+    isEditing = !editing;
+  };
 </script>
 
-<section class={`note-leather flex flex-col space-y-2 ${sectionClass}`}>
-  {#if depth < 4}
-    <Heading tag={getHeadingTag(depth)} class='h-leather'>{title}</Heading>
-    {#each orderedChildren as id, index}
-      {#if childIndices.includes(id)}
-        <svelte:self rootIndexId={id} depth={depth + 1} {allowEditing} />
-      {:else if (childZettels.includes(id))}
-        <div class='grid grid-cols-[1fr_auto] gap-2'>
-          <P class='note-leather' firstupper={index === 0}>
-            {@html $parser.getContent(id)}
-          </P>
-          {#if allowEditing}
-            <div class='flex flex-col space-y-2 justify-start'>
-              <Button class='btn-leather' size='sm' outline>
-                <CaretUpSolid />
-              </Button>
-              <Button class='btn-leather' size='sm' outline>
-                <CaretDownSolid />
-              </Button>
-              <Button class='btn-leather' size='sm' outline>
-                <EditOutline />
-              </Button>
-              <Tooltip class='tooltip-leather' type='auto' placement='top'>
-                Edit
-              </Tooltip>
-            </div>
-          {/if}
-        </div>
-      {/if}
-    {/each}
-  {:else}
-    <P class='note-leather' firstupper>
-      {@html $parser.getContent(rootIndexId)}
+<!-- This component is recursively structured.  The base case is single block of content. -->
+<!-- svelte-ignore a11y-no-static-element-interactions -->
+<section
+  id={rootId}
+  class={`note-leather w-full flex space-x-2 ${sectionClass}`}
+  on:mouseover={handleFocus}
+  on:focus={handleFocus}
+>
+  <!-- Zettel base case -->
+  {#if orderedChildren.length === 0 || depth >= 4}
+    <P firstupper={isSectionStart}>
+      {@html $parser.getContent(rootId)}
     </P>
+  {:else}
+    <div class='flex flex-col space-y-2'>
+      <Heading tag={getHeadingTag(depth)} class='h-leather'>
+        {title}
+      </Heading>
+      <!-- Recurse on child indices and zettels -->
+      {#each orderedChildren as id, index}
+        <svelte:self rootId={id} depth={depth + 1} {allowEditing} isSectionStart={index === 0} />
+      {/each}
+    </div>
+  {/if}
+  {#if allowEditing}
+    <div class={`flex flex-col space-y-2 justify-start ${$hoverTargetId === rootId ? 'visible' : 'invisible'}`}>
+      <Button class='btn-leather' size='sm' outline>
+        <CaretUpSolid />
+      </Button>
+      <Button class='btn-leather' size='sm' outline>
+        <CaretDownSolid />
+      </Button>
+      <Button class='btn-leather' size='sm' outline>
+        <EditOutline />
+      </Button>
+      <Tooltip class='tooltip-leather' type='auto' placement='top'>
+        Edit
+      </Tooltip>
+    </div>
+  {/if}
+</section>
+
+<!-- <section class={`note-leather grid grid-cols-[1fr_auto] gap-2 ${sectionClass}`}>
+  <div class={`flex flex-col space-y-2 ${depth > 0 ? 'border-l-gray-500 border-l pl-2' : ''}`}>
+    {#if depth < 4}
+      <Heading tag={getHeadingTag(depth)} class='h-leather'>{title}</Heading>
+      {#each orderedChildren as id, index}
+        {#if childIndices.includes(id)}
+          <svelte:self rootIndexId={id} depth={depth + 1} {allowEditing} />
+        {:else if (childZettels.includes(id))}
+          <div class='note-leather grid grid-cols-[1fr_auto] gap-2'>
+            {#if isEditing.get(id)}
+              <form>
+                <Textarea class='textarea-leather' rows={5} bind:value={editorContent[id]}>
+                  <div slot='footer' class='flex justify-end'>
+                    <Button class='btn-leather' size='sm' outline on:click={() => toggleEditing(id, false)}>
+                      Cancel
+                    </Button>
+                    <Button class='btn-leather' size='sm' on:click={() => toggleEditing(id)}>
+                      Save
+                    </Button>
+                  </div>
+                </Textarea>
+              </form>
+            {:else}
+              <P class='border-l-gray-500 border-l pl-2' firstupper={index === 0}>
+                {@html $parser.getContent(id)}
+              </P>
+            {/if}
+            {#if allowEditing}
+              <div class='col-start-2 flex flex-col space-y-2 justify-start'>
+                <Button class='btn-leather' size='sm' outline>
+                  <CaretUpSolid />
+                </Button>
+                <Button class='btn-leather' size='sm' outline>
+                  <CaretDownSolid />
+                </Button>
+                <Button class='btn-leather' size='sm' outline on:click={() => toggleEditing(id)}>
+                  <EditOutline />
+                </Button>
+                <Tooltip class='tooltip-leather' type='auto' placement='top'>
+                  Edit
+                </Tooltip>
+              </div>
+            {/if}
+          </div>
+        {/if}
+      {/each}
+    {:else}
+      <P class='note-leather' firstupper>
+        {@html $parser.getContent(rootIndexId)}
+      </P>
+    {/if}
+  </div>
+  {#if allowEditing}
+    <div class='col-start-2 flex flex-col space-y-2 justify-start'>
+      <Button class='btn-leather' size='sm' outline>
+        <CaretUpSolid />
+      </Button>
+      <Button class='btn-leather' size='sm' outline>
+        <CaretDownSolid />
+      </Button>
+      <Button class='btn-leather' size='sm' outline>
+        <EditOutline />
+      </Button>
+    </div>
   {/if}
-</section>
\ No newline at end of file
+</section> -->
\ No newline at end of file
diff --git a/src/lib/parser.ts b/src/lib/parser.ts
index 2bfb38e..ed05014 100644
--- a/src/lib/parser.ts
+++ b/src/lib/parser.ts
@@ -183,7 +183,7 @@ export default class Pharos {
    * @returns The IDs of any child indices of the index with the given ID.
    */
   getChildIndexIds(id: string): string[] {
-    return Array.from(this.indexToChildEventsMap.get(id)!)
+    return Array.from(this.indexToChildEventsMap.get(id) ?? [])
       .filter(id => this.eventToKindMap.get(id) === 30040);
   }
 
@@ -191,7 +191,7 @@ export default class Pharos {
    * @returns The IDs of any child zettels of the index with the given ID.
    */
   getChildZettelIds(id: string): string[] {
-    return Array.from(this.indexToChildEventsMap.get(id)!)
+    return Array.from(this.indexToChildEventsMap.get(id) ?? [])
       .filter(id => this.eventToKindMap.get(id) !== 30040);
   }
 
@@ -199,7 +199,7 @@ export default class Pharos {
    * @returns The IDs of any child nodes in the order in which they should be rendered.
    */
   getOrderedChildIds(id: string): string[] {
-    return Array.from(this.indexToChildEventsMap.get(id)!);
+    return Array.from(this.indexToChildEventsMap.get(id) ?? []);
   }
 
   /**
diff --git a/src/lib/stores.ts b/src/lib/stores.ts
index f072e5d..9b6bada 100644
--- a/src/lib/stores.ts
+++ b/src/lib/stores.ts
@@ -8,3 +8,5 @@ export let alexandriaKinds = readable<number[]>([30040, 30041]);
 export let feedType = writable<FeedType>(FeedType.Relays);
 
 export let editorText = writable<string>('');
+
+export let hoverTargetId = writable<string | null>(null);
diff --git a/src/routes/new/compose/+page.svelte b/src/routes/new/compose/+page.svelte
index a137d32..143ed9d 100644
--- a/src/routes/new/compose/+page.svelte
+++ b/src/routes/new/compose/+page.svelte
@@ -9,6 +9,6 @@
 <div class='w-full flex justify-center'>
   <main class='main-leather flex flex-col space-y-4 max-w-2xl w-full mt-4 mb-4'>
     <Heading tag='h1' class='h-leather mb-2'>Compose</Heading>
-    <Preview rootIndexId={$parser.getRootIndexId()} allowEditing={true} />
+    <Preview rootId={$parser.getRootIndexId()} allowEditing={true} />
   </main>
 </div>