diff --git a/src/App.css b/src/App.css
index 6798b71..10e7da8 100644
--- a/src/App.css
+++ b/src/App.css
@@ -27,6 +27,13 @@ input {
   margin-right: 10px;
 }
 
+select {
+  padding: 10px;
+  border: 1px solid #ccc;
+  border-radius: 4px;
+  margin-right: 10px;
+}
+
 button {
   padding: 10px 20px;
   border: none;
@@ -58,7 +65,6 @@ li {
 
 li span {
   flex: 1;
-  margin-right: 10px;
 }
 
 li span.completed {
@@ -68,16 +74,39 @@ li span.completed {
 
 .filter-buttons {
   display: flex;
-  justify-content: center;
   align-items: center;
+  justify-content: space-between;
+}
+
+.status-filter {
+  display: flex;
   gap: 10px;
 }
 
+.user-filter {
+  display: flex;
+  align-items: center;
+  margin-left: 20px;
+}
+
+.user-filter label {
+  margin-right: 10px;
+}
+
 .task-item {
   display: flex;
-  flex-direction: row;
-  justify-content: center;
+  flex-direction: column;
+}
+
+.task-item-header {
+  display: flex;
   align-items: center;
+  justify-content: space-between;
+  cursor: pointer;
+}
+
+.task-item-header .caret {
+  margin-left: 5px;
 }
 
 .task-item-buttons {
@@ -86,3 +115,24 @@ li span.completed {
   margin-left: auto;
   align-items: center;
 }
+
+.subtasks {
+  padding-left: 10px;
+  margin-top: 10px;
+}
+
+.subtask-item {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  margin-bottom: 5px;
+  flex-direction: row;
+}
+
+.subtask-input-container {
+  display: flex;
+  align-items: center;
+  gap: 10px;
+  margin-bottom: 10px;
+  flex-direction: row;
+}
diff --git a/src/App.jsx b/src/App.jsx
index 9144f05..259b681 100644
--- a/src/App.jsx
+++ b/src/App.jsx
@@ -11,35 +11,53 @@ function App() {
       name: "Complete TPS reports",
       completed: false,
       addedBy: { id: 1, name: "Kevin" },
+      subtasks: [],
     },
     {
       name: "Reconcile Dunder Mifflin accounts",
       completed: false,
       addedBy: { id: 2, name: "Angela" },
+      subtasks: [],
     },
     {
       name: "Review Peter's timesheet",
       completed: true,
-      addedBy: { id: 1, name: "Oscar" },
+      addedBy: { id: 3, name: "Oscar" },
+      subtasks: [],
     },
     {
       name: "Party Planning Committee expense reports",
       completed: false,
       addedBy: { id: 2, name: "Angela" },
+      subtasks: [],
     },
   ]);
   const [filter, setFilter] = useState("all");
+  const [userFilter, setUserFilter] = useState("all");
+
+  const users = tasks.reduce((users, task) => {
+    return users.includes(task.addedBy) ? users : [...users, task.addedBy];
+  }, []);
 
   return (
     <div>
       <Header />
       <div className="App">
         <div className="content">
-          <TaskForm setTasks={setTasks} />
+          <TaskForm setTasks={setTasks} users={users} />
         </div>
         <div className="content">
-          <FilterButtons setFilter={setFilter} />
-          <TaskList tasks={tasks} filter={filter} setTasks={setTasks} />
+          <FilterButtons
+            setFilter={setFilter}
+            setUserFilter={setUserFilter}
+            users={users}
+          />
+          <TaskList
+            tasks={tasks}
+            filter={filter}
+            userFilter={userFilter}
+            setTasks={setTasks}
+          />
         </div>
       </div>
     </div>
diff --git a/src/components/FilterButtons.jsx b/src/components/FilterButtons.jsx
index c69ebaa..365fff6 100644
--- a/src/components/FilterButtons.jsx
+++ b/src/components/FilterButtons.jsx
@@ -1,11 +1,18 @@
 import React from "react";
+import UserFilter from "./UserFilter";
 
-function FilterButtons({ setFilter }) {
+function FilterButtons({ setFilter, setUserFilter, users }) {
   return (
     <div className="filter-buttons">
-      <button onClick={() => setFilter("all")}>All</button>
-      <button onClick={() => setFilter("completed")}>Completed</button>
-      <button onClick={() => setFilter("incomplete")}>Incomplete</button>
+      <div className="status-filter">
+        <button onClick={() => setFilter("all")}>All</button>
+        <button onClick={() => setFilter("completed")}>Completed</button>
+        <button onClick={() => setFilter("incomplete")}>Incomplete</button>
+      </div>
+      <UserFilter
+        setUserFilter={(e) => setUserFilter(e.target.value)}
+        users={users}
+      />
     </div>
   );
 }
diff --git a/src/components/TaskForm.jsx b/src/components/TaskForm.jsx
index bde6a86..2c79459 100644
--- a/src/components/TaskForm.jsx
+++ b/src/components/TaskForm.jsx
@@ -1,19 +1,31 @@
 import React, { useState } from "react";
 
-function TaskForm({ setTasks }) {
+function TaskForm({ setTasks, users }) {
   const [taskName, setTaskName] = useState("");
+  const [selectedUser, setSelectedUser] = useState(users[0].id);
 
   const handleSubmit = (e) => {
     e.preventDefault();
+    const user = users.find((user) => user.id === selectedUser);
     setTasks((prevTasks) => [
       ...prevTasks,
-      { name: taskName, completed: false },
+      { name: taskName, completed: false, subtasks: [], addedBy: user },
     ]);
     setTaskName("");
   };
 
   return (
     <form onSubmit={handleSubmit}>
+      <select
+        onChange={(e) => setSelectedUser(parseInt(e.target.value, 10))}
+        value={selectedUser}
+      >
+        {users.map((user) => (
+          <option key={user.id} value={user.id}>
+            {user.name}
+          </option>
+        ))}
+      </select>
       <input
         type="text"
         value={taskName}
diff --git a/src/components/TaskItem.jsx b/src/components/TaskItem.jsx
index a8ca620..3f1d466 100644
--- a/src/components/TaskItem.jsx
+++ b/src/components/TaskItem.jsx
@@ -1,10 +1,14 @@
-import React from "react";
+import React, { useState, useEffect, useRef } from "react";
 
 function TaskItem({ task, index, setTasks }) {
-  const toggleCompletion = () => {
+  const [showSubtasks, setShowSubtasks] = useState(false);
+  const [newSubtask, setNewSubtask] = useState("");
+  const taskItemRef = useRef(null);
+
+  const toggeCompletion = () => {
     setTasks((prevTasks) =>
       prevTasks.map((t, i) =>
-        i === index ? { ...t, completed: !t.completed } : t
+        i === index ? { ...t, completed: !t.complted } : t
       )
     );
   };
@@ -13,17 +17,75 @@ function TaskItem({ task, index, setTasks }) {
     setTasks((prevTasks) => prevTasks.filter((_, i) => i !== index));
   };
 
+  const addSubtask = () => {
+    const newSubtaskObject = {
+      name: newSubtask,
+      completed: false,
+      subtasks: [],
+      addedBy: task.addedBy,
+    };
+    task.subtasks.push(newSubtaskObject);
+    setTasks((prevTasks) =>
+      prevTasks.map((t, i) =>
+        i === index ? { ...t, subtasks: task.subtasks } : t
+      )
+    );
+    setNewSubtask("");
+  };
+
+  const deleteSubtask = (subtaskIndex) => {
+    const updatedSubtasks = task.subtasks.filter((_, i) => i !== subtaskIndex);
+    setTasks((prevTasks) =>
+      prevTasks.map((t, i) =>
+        i === index ? { ...t, subtasks: updatedSubtasks } : t
+      )
+    );
+  };
+
+  useEffect(() => {
+    const currentRef = taskItemRef.current;
+    currentRef.addEventListener("click", () => setShowSubtasks(!showSubtasks));
+  }, []);
+
   return (
-    <li className="task-item">
-      <div className="task-item-header">
-        <span className={task.completed ? "completed" : ""}>{task.name}</span>
-      </div>
-      <div className="task-item-buttons">
-        <button onClick={toggleCompletion}>
-          {task.completed ? "Undo" : "Complete"}
-        </button>
-        <button onClick={deleteTask}>Delete</button>
-      </div>
+    <li className="task-item" ref={taskItemRef}>
+      <span className="task-item-header">
+        <span className={task.completed ? "completed" : undefined}>
+          {task.name} (Added by: {task.addedBy.name})
+        </span>
+        <div className="task-item-buttons">
+          <button onClick={toggeCompletion}>
+            {task.completed ? "Undo" : "Complete"}
+          </button>
+          <button onClick={deleteTask}>Delete</button>
+          <div className="caret">{showSubtasks ? "▼" : "▶"}</div>
+        </div>
+      </span>
+      {showSubtasks && (
+        <ul className="subtasks">
+          <div className="subtask-input-container">
+            <input
+              type="text"
+              value={newSubtask}
+              onChange={(e) => setNewSubtask(e.target.value)}
+              placeholder="Enter subtask"
+              onKeyDown={(e) => {
+                if (e.key === "Enter") {
+                  addSubtask();
+                }
+              }}
+            />
+            <button onClick={addSubtask}>Add Subtask</button>
+          </div>
+          {task.subtasks &&
+            task.subtasks.map((subtask, subIndex) => (
+              <li key={subIndex} className="subtask-item">
+                <span>{subtask.name}</span>
+                <button onClick={deleteSubtask(subIndex)}>Delete</button>
+              </li>
+            ))}
+        </ul>
+      )}
     </li>
   );
 }
diff --git a/src/components/TaskItem.test.jsx b/src/components/TaskItem.test.jsx
new file mode 100644
index 0000000..6db42da
--- /dev/null
+++ b/src/components/TaskItem.test.jsx
@@ -0,0 +1,23 @@
+import React from "react";
+import { render, fireEvent } from "@testing-library/react";
+import TaskItem from "./TaskItem";
+
+test("it should add a new subtask", () => {
+  const { getByPlaceholderText, getByText } = render(
+    <TaskItem
+      task={{
+        name: "Test Task",
+        completed: false,
+        subtasks: [],
+      }}
+      index={0}
+      setTasks={() => {}}
+    />
+  );
+
+  const taskItem = getByText("▶");
+  fireEvent.click(taskItem);
+  const input = getByPlaceholderText("Enter subtask");
+  fireEvent.change(input, { target: { value: "New Subtask" } });
+  fireEvent.keyDown(input, { key: "Enter", code: "Enter" });
+});
diff --git a/src/components/TaskList.jsx b/src/components/TaskList.jsx
index 3a9c0ae..29b1c14 100644
--- a/src/components/TaskList.jsx
+++ b/src/components/TaskList.jsx
@@ -1,13 +1,12 @@
 import React from "react";
 import TaskItem from "./TaskItem";
 
-function TaskList({ tasks, filter, setTasks }) {
-  const filteredTasks = tasks.filter((task) =>
-    filter === "all"
-      ? true
-      : filter === "completed"
-      ? task.completed
-      : !task.completed
+function TaskList({ tasks, filter, userFilter, setTasks }) {
+  const filteredTasks = tasks.filter(
+    (task) =>
+      (filter === "all" ||
+        (filter === "completed" ? task.completed : !task.completed)) &&
+      (userFilter === "all" || task.addedBy.id === parseInt(userFilter, 10))
   );
 
   return (
diff --git a/src/components/UserFilter.jsx b/src/components/UserFilter.jsx
new file mode 100644
index 0000000..d405000
--- /dev/null
+++ b/src/components/UserFilter.jsx
@@ -0,0 +1,17 @@
+import React from "react";
+
+function UserFilter({ setUserFilter, users }) {
+  return (
+    <div className="user-filter">
+      <label>Filter by user:</label>
+      <select onChange={setUserFilter}>
+        <option value="all">All</option>
+        {users.map((user) => (
+          <option value={user.id}>{user.name}</option>
+        ))}
+      </select>
+    </div>
+  );
+}
+
+export default UserFilter;