diff --git a/Server/Database/Database.cpp b/Server/Database/Database.cpp
index 0c915cc..492fa25 100644
--- a/Server/Database/Database.cpp
+++ b/Server/Database/Database.cpp
@@ -29,6 +29,8 @@ static int selectTaskCallback(void *data, int argc, char **argv, char **columnNa
             task.comment = argv[i];
         } else if (strcmp(columnName[i], "finished") == 0) {
             task.finished = std::atol(argv[i]);
+        } else if (strcmp(columnName[i], "parent_id") == 0) {
+            task.parentId = std::atol(argv[i]);
         }
     }
     tasks->push_back(task);
@@ -42,14 +44,27 @@ Tasks Database::tasks() {
         LOG(error) << "sqlite3_exec() failed: " << error << std::endl;
         sqlite3_free(error);
     }
+    std::unordered_map<int, Task *> tasks;
+    for (auto iterator = ret.begin(); iterator != ret.end();) {
+        if (iterator->parentId >= 0) {
+            auto parentTask = tasks.at(iterator->parentId);
+            parentTask->children.push_back(*iterator);
+            tasks.insert({iterator->id, &parentTask->children.back()});
+            iterator = ret.erase(iterator);
+        } else {
+            tasks.insert({iterator->id, &(*iterator)});
+            ++iterator;
+        }
+    }
     return ret;
 }
 
-bool Database::addTask(uint64_t createTime, const std::string &content, const std::string &comment, bool finished) {
+bool Database::addTask(uint64_t createTime, const std::string &content, const std::string &comment, int parentId,
+                       bool finished) {
     bool ret = true;
     std::ostringstream oss;
-    oss << "INSERT INTO tasks (create_time,content,comment,finished) VALUES (" << createTime << ",\"" << content
-        << "\",\"" << comment << "\"," << finished << ");";
+    oss << "INSERT INTO tasks (create_time,content,comment,parent_id,finished) VALUES (" << createTime << ",\""
+        << content << "\",\"" << comment << "\"," << parentId << "," << finished << ");";
     auto sql = oss.str();
     char *error = nullptr;
     int result = sqlite3_exec(m_sqlite3, sql.c_str(), NULL, NULL, &error);
diff --git a/Server/Database/Database.h b/Server/Database/Database.h
index 3de8a64..9906f81 100644
--- a/Server/Database/Database.h
+++ b/Server/Database/Database.h
@@ -14,7 +14,7 @@ public:
     ~Database();
     bool open(const std::string &path);
     Tasks tasks();
-    bool addTask(uint64_t createTime, const std::string &content, const std::string &comment = "",
+    bool addTask(uint64_t createTime, const std::string &content, const std::string &comment = "", int parentId = -1,
                  bool finished = false);
     bool removeTask(int id);
     void setTaskFinished(int id, bool finished, uint64_t finishedTime);
diff --git a/Server/Database/Task.cpp b/Server/Database/Task.cpp
index 32223b0..3798c70 100644
--- a/Server/Database/Task.cpp
+++ b/Server/Database/Task.cpp
@@ -5,16 +5,28 @@
 
 namespace boost {
 namespace json {
+
+static boost::json::object serialize(const Task &task) {
+    boost::json::object ret;
+    ret["id"] = task.id;
+    ret["parentId"] = task.parentId;
+    ret["finished"] = task.finished;
+    ret["createTime"] = task.createTime;
+    ret["content"] = task.content;
+    ret["comment"] = task.comment;
+
+    boost::json::array children;
+    for (auto &child : task.children) {
+        children.push_back(serialize(child));
+    }
+    ret["children"] = std::move(children);
+    return ret;
+}
+
 std::string serialize(const Tasks &tasks) {
     boost::json::array ret;
     for (auto &task : tasks) {
-        boost::json::object t;
-        t["id"] = task.id;
-        t["finished"] = task.finished;
-        t["createTime"] = task.createTime;
-        t["content"] = task.content;
-        t["comment"] = task.comment;
-        ret.push_back(std::move(t));
+        ret.push_back(serialize(task));
     }
     return boost::json::serialize(ret);
 }
diff --git a/Server/Database/Task.h b/Server/Database/Task.h
index 5f21182..445173a 100644
--- a/Server/Database/Task.h
+++ b/Server/Database/Task.h
@@ -4,15 +4,19 @@
 #include <list>
 #include <string>
 
+class Task;
+using Tasks = std::list<Task>;
+
 class Task {
 public:
     int id = -1;
+    int parentId = -1;
     bool finished = false;
     int32_t createTime = 0;
     std::string content;
     std::string comment;
+    Tasks children;
 };
-using Tasks = std::list<Task>;
 
 namespace boost {
 namespace json {
diff --git a/Server/SharedState.cpp b/Server/SharedState.cpp
index 6757614..037ee40 100644
--- a/Server/SharedState.cpp
+++ b/Server/SharedState.cpp
@@ -70,7 +70,7 @@ SharedState::SharedState(boost::asio::io_context &ioContext, std::string doc_roo
         auto database = Amass::Singleton<Database>::instance();
         auto root = boost::json::parse(request.body());
         bool ret = database->addTask(root.at("createTime").as_int64(), std::string(root.at("content").as_string()),
-                                        std::string(root.at("comment").as_string()));
+                                        std::string(root.at("comment").as_string()), root.at("parentId").as_int64());
         boost::json::object reply;
         reply["status"] = ret ? 0 : -1;
         http::response<boost::beast::http::string_body> s{boost::beast::http::status::ok, request.version()};