diff --git a/crates/loro-internal/src/container/list/list_container.rs b/crates/loro-internal/src/container/list/list_container.rs
index c4c3d506..e3935bee 100644
--- a/crates/loro-internal/src/container/list/list_container.rs
+++ b/crates/loro-internal/src/container/list/list_container.rs
@@ -684,12 +684,9 @@ impl List {
         self.with_container(|list| list.iter().enumerate().for_each(f))
     }
 
-    // pub fn map<F: FnMut(&LoroValue) -> R, R>(
-    //     &self,
-    //     f: F,
-    // ) -> Map<impl Iterator<Item = &LoroValue>, F> {
-    //     self.with_container(|list| list.iter().map(f))
-    // }
+    pub fn map<F: FnMut((usize, &LoroValue)) -> R, R>(&self, f: F) -> Vec<R> {
+        self.with_container(|list| list.iter().enumerate().map(f).collect())
+    }
 
     #[must_use]
     pub fn is_empty(&self) -> bool {
@@ -735,7 +732,7 @@ impl ContainerWrapper for List {
 
 #[cfg(test)]
 mod test {
-    use crate::LoroCore;
+    use crate::{LoroCore, LoroValue, PrelimContainer};
 
     #[test]
     fn test_list_get() {
@@ -787,4 +784,16 @@ mod test {
             assert_eq!(format!("\"{c}\""), v.to_json())
         })
     }
+
+    #[test]
+    fn map() {
+        let mut loro = LoroCore::default();
+        let mut list = loro.get_list("list");
+        list.insert(&loro, 0, "a").unwrap();
+        list.insert(&loro, 1, "b").unwrap();
+        list.insert(&loro, 2, "c").unwrap();
+        // list.insert(&loro, 3, PrelimContainer::from("hello".to_string()))
+        //     .unwrap();
+        assert_eq!(list.map(|(_, v)| v.to_json()),vec!["\"a\"", "\"b\"", "\"c\""]);
+    }
 }
diff --git a/crates/loro-internal/src/error.rs b/crates/loro-internal/src/error.rs
index b8379083..547ba2ef 100644
--- a/crates/loro-internal/src/error.rs
+++ b/crates/loro-internal/src/error.rs
@@ -16,6 +16,8 @@ pub enum LoroError {
     LockError,
     #[error("LoroValue::Unresolved cannot be converted to PrelimValue")]
     PrelimError,
+    #[error("Cannot find ({0}) ")]
+    NotFoundError(Box<str>),
     // #[error("the data for key `{0}` is not available")]
     // Redaction(String),
     // #[error("invalid header (expected {expected:?}, found {found:?})")]
diff --git a/crates/loro-internal/src/hierarchy.rs b/crates/loro-internal/src/hierarchy.rs
index e2b49667..306b9f6b 100644
--- a/crates/loro-internal/src/hierarchy.rs
+++ b/crates/loro-internal/src/hierarchy.rs
@@ -8,6 +8,7 @@ use fxhash::{FxHashMap, FxHashSet};
 use crate::{
     container::{registry::ContainerRegistry, ContainerID},
     event::{Event, EventDispatch, Index, Observer, Path, PathAndTarget, RawEvent, SubscriptionID},
+    LoroError,
 };
 
 /// [`Hierarchy`] stores the hierarchical relationship between containers
@@ -78,6 +79,20 @@ impl Hierarchy {
             .unwrap_or(false)
     }
 
+    pub fn children(&self, id: &ContainerID) -> Result<FxHashSet<ContainerID>, LoroError> {
+        self.nodes
+            .get(id)
+            .ok_or(LoroError::NotFoundError(format!("{:?}", id).into()))
+            .map(|node| node.children.clone())
+    }
+
+    pub fn parent(&self, id: &ContainerID) -> Result<Option<ContainerID>, LoroError> {
+        self.nodes
+            .get(id)
+            .ok_or(LoroError::NotFoundError(format!("{:?}", id).into()))
+            .map(|node| node.parent.clone())
+    }
+
     #[inline(always)]
     pub fn contains(&self, id: &ContainerID) -> bool {
         self.nodes.get(id).is_some() || id.is_root()
@@ -429,3 +444,32 @@ impl Hierarchy {
         }
     }
 }
+
+#[cfg(test)]
+mod test {
+    use fxhash::FxHashMap;
+
+    use crate::{LoroCore, PrelimContainer};
+
+    #[test]
+    fn children_parent() {
+        let mut loro = LoroCore::default();
+        let mut list = loro.get_list("list");
+        let map_container_id = list
+            .push(&loro, PrelimContainer::from(FxHashMap::default()))
+            .unwrap()
+            .unwrap();
+        let list_container_id = list.id();
+        assert_eq!(
+            loro.children(&list_container_id)
+                .unwrap()
+                .into_iter()
+                .collect::<Vec<_>>(),
+            vec![map_container_id.clone()]
+        );
+        assert_eq!(
+            loro.parent(&map_container_id).unwrap().unwrap(),
+            list_container_id
+        )
+    }
+}
diff --git a/crates/loro-internal/src/loro.rs b/crates/loro-internal/src/loro.rs
index eeca1422..cc29dfda 100644
--- a/crates/loro-internal/src/loro.rs
+++ b/crates/loro-internal/src/loro.rs
@@ -7,7 +7,7 @@ use crate::{
     log_store::{EncodeConfig, LoroEncoder},
     LoroError, LoroValue,
 };
-use fxhash::FxHashMap;
+use fxhash::{FxHashMap, FxHashSet};
 use tracing::instrument;
 
 use crate::{
@@ -79,6 +79,16 @@ impl LoroCore {
         store.contains_container(id)
     }
 
+    pub fn children(&self, id: &ContainerID) -> Result<FxHashSet<ContainerID>, LoroError> {
+        let hierarchy = self.hierarchy.try_lock().unwrap();
+        hierarchy.children(id)
+    }
+
+    pub fn parent(&self, id: &ContainerID) -> Result<Option<ContainerID>, LoroError> {
+        let hierarchy = self.hierarchy.try_lock().unwrap();
+        hierarchy.parent(id)
+    }
+
     // TODO: make it private
     pub fn export(&self, remote_vv: VersionVector) -> FxHashMap<u64, Vec<Change<RemoteOp>>> {
         let store = self.log_store.read().unwrap();