diff --git a/thoughts-frontend/app/page.tsx b/thoughts-frontend/app/page.tsx
index 20ee490..c5c1a33 100644
--- a/thoughts-frontend/app/page.tsx
+++ b/thoughts-frontend/app/page.tsx
@@ -1,11 +1,13 @@
 // app/page.tsx
 import { cookies } from "next/headers";
-import { getFeed, getMe, getUserProfile, Me } from "@/lib/api";
+import { getFeed, getMe, getUserProfile, Me, Thought } from "@/lib/api";
 import { ThoughtCard } from "@/components/thought-card";
 import { PostThoughtForm } from "@/components/post-thought-form";
 import { Button } from "@/components/ui/button";
 import Link from "next/link";
 import { PopularTags } from "@/components/popular-tags";
+import { ThoughtThread } from "@/components/thought-thread";
+import { buildThoughtThreads } from "@/lib/utils";
 
 // This is now an async Server Component
 export default async function Home() {
@@ -32,6 +34,10 @@ async function FeedPage({ token }: { token: string }) {
       .map((user) => [user!.username, { avatarUrl: user!.avatarUrl }])
   );
 
+  const allThoughts = feedData.thoughts;
+  const { topLevelThoughts, repliesByParentId } =
+    buildThoughtThreads(allThoughts);
+
   return (
     <div className="container mx-auto max-w-4xl p-4 sm:p-6 grid grid-cols-1 md:grid-cols-3 gap-8">
       <main className="md:col-span-2 space-y-6">
@@ -39,22 +45,22 @@ async function FeedPage({ token }: { token: string }) {
           <h1 className="text-3xl font-bold">Your Feed</h1>
         </header>
         <PostThoughtForm />
-        {feedData.thoughts.map((thought) => (
-          <ThoughtCard
-            key={thought.id}
-            thought={thought}
-            author={{
-              username: thought.authorUsername,
-              avatarUrl: authorDetails.get(thought.authorUsername)?.avatarUrl,
-            }}
-            currentUser={me}
-          />
-        ))}
-        {feedData.thoughts.length === 0 && (
-          <p className="text-center text-muted-foreground pt-8">
-            Your feed is empty. Follow some users to see their thoughts here!
-          </p>
-        )}
+        <main className="space-y-6">
+          {topLevelThoughts.map((thought) => (
+            <ThoughtThread
+              key={thought.id}
+              thought={thought}
+              repliesByParentId={repliesByParentId}
+              authorDetails={authorDetails}
+              currentUser={me}
+            />
+          ))}
+          {topLevelThoughts.length === 0 && (
+            <p className="text-center text-muted-foreground pt-8">
+              Your feed is empty. Follow some users to see their thoughts here!
+            </p>
+          )}
+        </main>
       </main>
       <aside className="md:col-span-1 space-y-6 pt-20">
         <PopularTags />
diff --git a/thoughts-frontend/app/users/[username]/page.tsx b/thoughts-frontend/app/users/[username]/page.tsx
index 74219a4..1e0ce06 100644
--- a/thoughts-frontend/app/users/[username]/page.tsx
+++ b/thoughts-frontend/app/users/[username]/page.tsx
@@ -1,12 +1,13 @@
 import { getMe, getUserProfile, getUserThoughts, Me } from "@/lib/api";
 import { UserAvatar } from "@/components/user-avatar";
-import { ThoughtCard } from "@/components/thought-card";
 import { Calendar } from "lucide-react";
 import { Card } from "@/components/ui/card";
 import { notFound } from "next/navigation";
 import { cookies } from "next/headers";
 import { FollowButton } from "@/components/follow-button";
 import { TopFriends } from "@/components/top-friends";
+import { buildThoughtThreads } from "@/lib/utils";
+import { ThoughtThread } from "@/components/thought-thread";
 
 interface ProfilePageProps {
   params: { username: string };
@@ -16,10 +17,8 @@ export default async function ProfilePage({ params }: ProfilePageProps) {
   const { username } = params;
   const token = (await cookies()).get("auth_token")?.value ?? null;
 
-  // Fetch data in parallel
   const userProfilePromise = getUserProfile(username, token);
   const thoughtsPromise = getUserThoughts(username, token);
-  // Fetch the logged-in user's data (if they exist)
   const mePromise = token ? getMe(token) : Promise.resolve(null);
 
   const [userResult, thoughtsResult, meResult] = await Promise.allSettled([
@@ -33,26 +32,27 @@ export default async function ProfilePage({ params }: ProfilePageProps) {
   }
 
   const user = userResult.value;
-  const thoughts =
-    thoughtsResult.status === "fulfilled" ? thoughtsResult.value.thoughts : [];
   const me = meResult.status === "fulfilled" ? (meResult.value as Me) : null;
 
-  // *** SIMPLIFIED LOGIC ***
-  // The follow status is now directly available from the `me` object.
+  const thoughts =
+    thoughtsResult.status === "fulfilled" ? thoughtsResult.value.thoughts : [];
+  const { topLevelThoughts, repliesByParentId } = buildThoughtThreads(thoughts);
+
   const isOwnProfile = me?.username === user.username;
   const isFollowing =
     me?.following?.some(
       (followedUser) => followedUser.username === user.username
     ) || false;
 
+  const authorDetails = new Map<string, { avatarUrl?: string | null }>();
+  authorDetails.set(user.username, { avatarUrl: user.avatarUrl });
+
   return (
     <div>
-      {/* Custom CSS Injection */}
       {user.customCss && (
         <style dangerouslySetInnerHTML={{ __html: user.customCss }} />
       )}
 
-      {/* Header Image */}
       <div
         className="h-48 bg-gray-200 bg-cover bg-center"
         style={{
@@ -81,7 +81,6 @@ export default async function ProfilePage({ params }: ProfilePageProps) {
                 </div>
               </div>
 
-              {/* Render the FollowButton if it's not the user's own profile */}
               {!isOwnProfile && token && (
                 <FollowButton
                   username={user.username}
@@ -99,17 +98,19 @@ export default async function ProfilePage({ params }: ProfilePageProps) {
 
           {/* Thoughts Feed */}
           <div className="mt-8 space-y-4">
-            {thoughts.map((thought) => (
-              <ThoughtCard
+            {topLevelThoughts.map((thought) => (
+              <ThoughtThread
                 key={thought.id}
                 thought={thought}
-                author={{ username: user.username, avatarUrl: user.avatarUrl }}
-                currentUser={me || null}
+                repliesByParentId={repliesByParentId}
+                authorDetails={authorDetails}
+                currentUser={me}
               />
             ))}
-            {thoughts.length === 0 && (
-              <p className="text-center text-muted-foreground">
-                This user hasn&apos;t posted any thoughts yet.
+            {topLevelThoughts.length === 0 && (
+              <p className="text-center text-muted-foreground pt-8">
+                Your feed is empty. Follow some users to see their thoughts
+                here!
               </p>
             )}
           </div>
diff --git a/thoughts-frontend/components/reply-form.tsx b/thoughts-frontend/components/reply-form.tsx
new file mode 100644
index 0000000..3900edf
--- /dev/null
+++ b/thoughts-frontend/components/reply-form.tsx
@@ -0,0 +1,90 @@
+// components/reply-form.tsx
+"use client";
+
+import { useForm } from "react-hook-form";
+import { zodResolver } from "@hookform/resolvers/zod";
+import { z } from "zod";
+import { useRouter } from "next/navigation";
+import { Button } from "@/components/ui/button";
+import {
+  Form,
+  FormField,
+  FormItem,
+  FormControl,
+  FormMessage,
+} from "@/components/ui/form";
+import { Textarea } from "@/components/ui/textarea";
+import { CreateThoughtSchema, createThought } from "@/lib/api";
+import { useAuth } from "@/hooks/use-auth";
+import { toast } from "sonner";
+
+interface ReplyFormProps {
+  parentThoughtId: string;
+  onReplySuccess: () => void; // A callback to close the form after success
+}
+
+export function ReplyForm({ parentThoughtId, onReplySuccess }: ReplyFormProps) {
+  const router = useRouter();
+  const { token } = useAuth();
+
+  const form = useForm<z.infer<typeof CreateThoughtSchema>>({
+    resolver: zodResolver(CreateThoughtSchema),
+    defaultValues: {
+      content: "",
+      replyToId: parentThoughtId,
+      visibility: "Public", // Replies default to Public
+    },
+  });
+
+  async function onSubmit(values: z.infer<typeof CreateThoughtSchema>) {
+    if (!token) {
+      toast.error("You must be logged in to reply.");
+      return;
+    }
+
+    try {
+      await createThought(values, token);
+      toast.success("Your reply has been posted!");
+      form.reset();
+      onReplySuccess(); // Call the callback
+      router.refresh(); // Refresh the page to show the new reply
+    } catch (err) {
+      toast.error("Failed to post reply. Please try again.");
+    }
+  }
+
+  return (
+    <Form {...form}>
+      <form onSubmit={form.handleSubmit(onSubmit)} className="space-y-2 pt-4">
+        <FormField
+          control={form.control}
+          name="content"
+          render={({ field }) => (
+            <FormItem>
+              <FormControl>
+                <Textarea
+                  placeholder="Post your reply..."
+                  className="resize-none"
+                  {...field}
+                />
+              </FormControl>
+              <FormMessage />
+            </FormItem>
+          )}
+        />
+        <div className="flex justify-end gap-2">
+          <Button
+            type="button"
+            variant="ghost"
+            onClick={onReplySuccess} // Close button
+          >
+            Cancel
+          </Button>
+          <Button type="submit" disabled={form.formState.isSubmitting}>
+            {form.formState.isSubmitting ? "Replying..." : "Reply"}
+          </Button>
+        </div>
+      </form>
+    </Form>
+  );
+}
diff --git a/thoughts-frontend/components/thought-card.tsx b/thoughts-frontend/components/thought-card.tsx
index 0fa3ca1..6ec6766 100644
--- a/thoughts-frontend/components/thought-card.tsx
+++ b/thoughts-frontend/components/thought-card.tsx
@@ -1,6 +1,11 @@
 "use client";
 
-import { Card, CardContent, CardHeader } from "@/components/ui/card";
+import {
+  Card,
+  CardContent,
+  CardFooter,
+  CardHeader,
+} from "@/components/ui/card";
 import { UserAvatar } from "./user-avatar";
 import { deleteThought, Me, Thought } from "@/lib/api";
 import { formatDistanceToNow } from "date-fns";
@@ -14,6 +19,7 @@ import {
   DropdownMenuItem,
   DropdownMenuTrigger,
 } from "@/components/ui/dropdown-menu";
+import { Button } from "@/components/ui/button";
 import {
   AlertDialog,
   AlertDialogAction,
@@ -24,7 +30,14 @@ import {
   AlertDialogHeader,
   AlertDialogTitle,
 } from "@/components/ui/alert-dialog";
-import { MoreHorizontal, Trash2 } from "lucide-react";
+import {
+  CornerUpLeft,
+  MessageSquare,
+  MoreHorizontal,
+  Trash2,
+} from "lucide-react";
+import { ReplyForm } from "@/components/reply-form";
+import Link from "next/link";
 
 interface ThoughtCardProps {
   thought: Thought;
@@ -33,14 +46,17 @@ interface ThoughtCardProps {
     avatarUrl?: string | null;
   };
   currentUser: Me | null;
+  isReply?: boolean;
 }
 
 export function ThoughtCard({
   thought,
   author,
   currentUser,
+  isReply = false,
 }: ThoughtCardProps) {
   const [isAlertOpen, setIsAlertOpen] = useState(false);
+  const [isReplyOpen, setIsReplyOpen] = useState(false);
   const { token } = useAuth();
   const router = useRouter();
   const timeAgo = formatDistanceToNow(new Date(thought.createdAt), {
@@ -64,6 +80,25 @@ export function ThoughtCard({
 
   return (
     <>
+      <div
+        id={thought.id}
+        className={!isReply ? "bg-card rounded-xl border shadow-sm" : ""}
+      >
+        {thought.replyToId && isReply && (
+          <div className="px-4 pt-2 text-sm text-muted-foreground flex items-center gap-2">
+            <CornerUpLeft className="h-4 w-4" />
+            <span>
+              Replying to{" "}
+              <Link
+                href={`#${thought.replyToId}`}
+                className="hover:underline text-primary"
+              >
+                parent thought
+              </Link>
+            </span>
+          </div>
+        )}
+      </div>
       <Card>
         <CardHeader className="flex flex-row items-center justify-between space-y-0">
           <div className="flex items-center gap-4">
@@ -95,6 +130,26 @@ export function ThoughtCard({
         <CardContent>
           <p className="whitespace-pre-wrap break-words">{thought.content}</p>
         </CardContent>
+
+        <CardFooter className="border-t px-4 pt-2 pb-2">
+          <Button
+            variant="ghost"
+            size="sm"
+            onClick={() => setIsReplyOpen(!isReplyOpen)}
+          >
+            <MessageSquare className="mr-2 h-4 w-4" />
+            Reply
+          </Button>
+        </CardFooter>
+
+        {isReplyOpen && (
+          <div className="border-t p-4">
+            <ReplyForm
+              parentThoughtId={thought.id}
+              onReplySuccess={() => setIsReplyOpen(false)}
+            />
+          </div>
+        )}
       </Card>
       <AlertDialog open={isAlertOpen} onOpenChange={setIsAlertOpen}>
         <AlertDialogContent>
diff --git a/thoughts-frontend/components/thought-thread.tsx b/thoughts-frontend/components/thought-thread.tsx
new file mode 100644
index 0000000..3de3aca
--- /dev/null
+++ b/thoughts-frontend/components/thought-thread.tsx
@@ -0,0 +1,52 @@
+import { Me, Thought } from "@/lib/api";
+import { ThoughtCard } from "./thought-card";
+
+interface ThoughtThreadProps {
+  thought: Thought;
+  repliesByParentId: Map<string, Thought[]>;
+  authorDetails: Map<string, { avatarUrl?: string | null }>;
+  currentUser: Me | null;
+  isReply?: boolean;
+}
+
+export function ThoughtThread({
+  thought,
+  repliesByParentId,
+  authorDetails,
+  currentUser,
+  isReply = false,
+}: ThoughtThreadProps) {
+  const author = {
+    username: thought.authorUsername,
+    avatarUrl: null,
+    ...authorDetails.get(thought.authorUsername),
+  };
+
+  const directReplies = repliesByParentId.get(thought.id) || [];
+
+  return (
+    <div className="flex flex-col gap-0">
+      <ThoughtCard
+        thought={thought}
+        author={author}
+        currentUser={currentUser}
+        isReply={isReply}
+      />
+
+      {directReplies.length > 0 && (
+        <div className="pl-6 border-l-2 border-dashed ml-6 flex flex-col gap-4 pt-4">
+          {directReplies.map((reply) => (
+            <ThoughtThread // RECURSIVE CALL
+              key={reply.id}
+              thought={reply}
+              repliesByParentId={repliesByParentId} // Pass the full map down
+              authorDetails={authorDetails}
+              currentUser={currentUser}
+              isReply={true}
+            />
+          ))}
+        </div>
+      )}
+    </div>
+  );
+}
diff --git a/thoughts-frontend/lib/utils.ts b/thoughts-frontend/lib/utils.ts
index bd0c391..64f24df 100644
--- a/thoughts-frontend/lib/utils.ts
+++ b/thoughts-frontend/lib/utils.ts
@@ -1,6 +1,35 @@
 import { clsx, type ClassValue } from "clsx"
 import { twMerge } from "tailwind-merge"
+import { Thought } from "./api";
 
 export function cn(...inputs: ClassValue[]) {
   return twMerge(clsx(inputs))
 }
+
+export function buildThoughtThreads(allThoughts: Thought[]) {
+  const repliesByParentId = new Map<string, Thought[]>();
+  const topLevelThoughts: Thought[] = [];
+
+  // 1. Group all thoughts into top-level posts or replies
+  for (const thought of allThoughts) {
+    if (thought.replyToId) {
+      // It's a reply, group it with its parent
+      const replies = repliesByParentId.get(thought.replyToId) || [];
+      replies.push(thought);
+      repliesByParentId.set(thought.replyToId, replies);
+    } else {
+      // It's a top-level thought
+      topLevelThoughts.push(thought);
+    }
+  }
+
+  // 2. Sort top-level thoughts by date, newest first
+  topLevelThoughts.sort((a, b) => new Date(b.createdAt).getTime() - new Date(a.createdAt).getTime());
+
+  // 3. Sort replies within each thread by date, oldest first for conversational flow
+  for (const replies of repliesByParentId.values()) {
+    replies.sort((a, b) => new Date(a.createdAt).getTime() - new Date(b.createdAt).getTime());
+  }
+
+  return { topLevelThoughts, repliesByParentId };
+}
\ No newline at end of file