diff --git a/nutree/common.py b/nutree/common.py
index cc65229..42ac785 100644
--- a/nutree/common.py
+++ b/nutree/common.py
@@ -13,6 +13,7 @@
 import sys
 import warnings
 import zipfile
+from collections.abc import Iterator
 from contextlib import contextmanager
 from enum import Enum
 from pathlib import Path
@@ -21,11 +22,7 @@
     TYPE_CHECKING,
     Any,
     Callable,
-    Dict,
-    Iterator,
-    List,
     Literal,
-    Type,
     Union,
 )
 
@@ -129,17 +126,17 @@ def __init__(self, value=None):
 ReprArgType = Union[str, Callable[["Node"], str]]
 
 #: A dict of scalar values
-FlatJsonDictType = Dict[str, Union[str, int, float, bool, None]]
+FlatJsonDictType = dict[str, Union[str, int, float, bool, None]]
 
 #: Type of ``tree.save(..., key_map)``
-KeyMapType = Dict[str, str]
+KeyMapType = dict[str, str]
 
 #: Type of ``tree.save(..., value_map)``
 #: E.g. `{'t': ['person', 'dept']}`
-ValueMapType = Dict[str, List[str]]
+ValueMapType = dict[str, list[str]]
 
 #: E.g. `{'t': {'person': 0, 'dept': 1}}`
-ValueDictMapType = Dict[str, Dict[str, int]]
+ValueDictMapType = dict[str, dict[str, int]]
 
 #: Generic callback for `tree.to_dot()`, ...
 MapperCallbackType = Callable[["Node", dict], Union[None, Any]]
@@ -152,7 +149,7 @@ def __init__(self, value=None):
 
 #: Generic callback for `tree.filter()`, `tree.copy()`, ...
 PredicateCallbackType = Callable[
-    ["Node"], Union[None, bool, IterationControl, Type[IterationControl]]
+    ["Node"], Union[None, bool, IterationControl, type[IterationControl]]
 ]
 
 #:
@@ -166,9 +163,9 @@ def __init__(self, value=None):
         bool,
         SkipBranch,
         StopTraversal,
-        Type[SkipBranch],
-        Type[StopTraversal],
-        Type[StopIteration],
+        type[SkipBranch],
+        type[StopTraversal],
+        type[StopIteration],
     ],
 ]
 #: Callback for `tree.sort(key=...)`
diff --git a/nutree/dot.py b/nutree/dot.py
index 7c0dc9a..c2b678d 100644
--- a/nutree/dot.py
+++ b/nutree/dot.py
@@ -7,8 +7,9 @@
 
 from __future__ import annotations
 
+from collections.abc import Iterator
 from pathlib import Path
-from typing import IO, TYPE_CHECKING, Any, Iterator
+from typing import IO, TYPE_CHECKING, Any
 
 from nutree.common import MapperCallbackType, call_mapper
 
diff --git a/nutree/mermaid.py b/nutree/mermaid.py
index 5d8d78b..b53695a 100644
--- a/nutree/mermaid.py
+++ b/nutree/mermaid.py
@@ -9,9 +9,10 @@
 from __future__ import annotations
 
 import io
+from collections.abc import Iterable, Iterator
 from pathlib import Path
 from subprocess import CalledProcessError, check_output
-from typing import IO, TYPE_CHECKING, Callable, Iterable, Iterator, Literal
+from typing import IO, TYPE_CHECKING, Callable, Literal
 
 from nutree.common import DataIdType
 
diff --git a/nutree/node.py b/nutree/node.py
index c83681c..07fbfd5 100644
--- a/nutree/node.py
+++ b/nutree/node.py
@@ -13,6 +13,7 @@
 from __future__ import annotations
 
 import re
+from collections.abc import Iterable, Iterator
 from operator import attrgetter
 from pathlib import Path
 from typing import (
@@ -20,8 +21,6 @@
     TYPE_CHECKING,
     Any,
     Generic,
-    Iterable,
-    Iterator,
     cast,
 )
 
diff --git a/nutree/tree.py b/nutree/tree.py
index 0eef9d8..2945fae 100644
--- a/nutree/tree.py
+++ b/nutree/tree.py
@@ -15,15 +15,13 @@
 import json
 import random
 import threading
+from collections.abc import Iterable, Iterator
 from pathlib import Path
 from typing import (
     IO,
     Any,
     Generic,
-    Iterable,
-    Iterator,
     Literal,
-    Type,
     Union,
     cast,
 )
@@ -111,7 +109,7 @@ class Tree(Generic[TData, TNode]):
     **Note:** Use with care, see also :ref:`forward-attributes`.
     """
 
-    node_factory: Type[TNode] = cast(Type[TNode], Node)
+    node_factory: type[TNode] = cast(type[TNode], Node)
     root_node_factory = _SystemRootNode
 
     #: Default connector prefixes ``format(style=...)`` argument.
diff --git a/nutree/tree_generator.py b/nutree/tree_generator.py
index 9aece65..73748c0 100644
--- a/nutree/tree_generator.py
+++ b/nutree/tree_generator.py
@@ -9,8 +9,9 @@
 import random
 import sys
 from abc import ABC, abstractmethod
+from collections.abc import Sequence
 from datetime import date, datetime, timedelta, timezone
-from typing import Any, Sequence, Union
+from typing import Any, Union
 
 from nutree.common import DictWrapper
 from nutree.node import Node
diff --git a/nutree/typed_tree.py b/nutree/typed_tree.py
index 6581f56..8925bf9 100644
--- a/nutree/typed_tree.py
+++ b/nutree/typed_tree.py
@@ -15,8 +15,9 @@
 from __future__ import annotations
 
 from collections import Counter
+from collections.abc import Iterator
 from pathlib import Path
-from typing import IO, Iterator, Type, cast, final
+from typing import IO, cast, final
 
 # typing.Self requires Python 3.11
 from typing_extensions import Any, Self
@@ -100,7 +101,7 @@ def __repr__(self) -> str:
     def kind(self) -> str:
         return self._kind
 
-    def get_children(self, kind: str | Type[ANY_KIND]) -> list[Self]:
+    def get_children(self, kind: str | type[ANY_KIND]) -> list[Self]:
         """Return list of direct child nodes of a given type (list may be empty)."""
         all_children = self._children
         if not all_children:
@@ -109,7 +110,7 @@ def get_children(self, kind: str | Type[ANY_KIND]) -> list[Self]:
             return all_children
         return list(filter(lambda n: n._kind == kind, all_children))
 
-    def first_child(self, kind: str | Type[ANY_KIND]) -> Self | None:
+    def first_child(self, kind: str | type[ANY_KIND]) -> Self | None:
         """First direct child node or None if no children exist."""
         all_children = self._children
         if not all_children:
@@ -122,7 +123,7 @@ def first_child(self, kind: str | Type[ANY_KIND]) -> Self | None:
                 return n
         return None
 
-    def last_child(self, kind: str | Type[ANY_KIND]) -> Self | None:
+    def last_child(self, kind: str | type[ANY_KIND]) -> Self | None:
         """Last direct child node or None if no children exist."""
         all_children = self._children
         if not all_children:
@@ -136,7 +137,7 @@ def last_child(self, kind: str | Type[ANY_KIND]) -> Self | None:
                 return n
         return None
 
-    def has_children(self, kind: str | Type[ANY_KIND]) -> bool:
+    def has_children(self, kind: str | type[ANY_KIND]) -> bool:
         """Return true if this node has one or more children."""
         if kind is ANY_KIND:
             return bool(self._children)
@@ -283,7 +284,7 @@ def add_child(
 
         source_node: Self = None  # type: ignore
         new_node: Self = None  # type: ignore
-        factory: Type[Self] = self._tree.node_factory  # type: ignore
+        factory: type[Self] = self._tree.node_factory  # type: ignore
 
         if isinstance(child, TypedNode):
             if deep is None:
@@ -620,15 +621,15 @@ def add(
             node_id=node_id,
         )
 
-    def first_child(self, kind: str | Type[ANY_KIND]) -> TypedNode[TData] | None:
+    def first_child(self, kind: str | type[ANY_KIND]) -> TypedNode[TData] | None:
         """Return the first toplevel node."""
         return self.system_root.first_child(kind=kind)
 
-    def last_child(self, kind: str | Type[ANY_KIND]) -> TypedNode[TData] | None:
+    def last_child(self, kind: str | type[ANY_KIND]) -> TypedNode[TData] | None:
         """Return the last toplevel node."""
         return self.system_root.last_child(kind=kind)
 
-    def iter_by_type(self, kind: str | Type[ANY_KIND]) -> Iterator[TypedNode[TData]]:
+    def iter_by_type(self, kind: str | type[ANY_KIND]) -> Iterator[TypedNode[TData]]:
         if kind == ANY_KIND:
             yield from self.iterator()
         for n in self.iterator():
diff --git a/pyproject.toml b/pyproject.toml
index 6a02e3a..9aadbbd 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 # --- Ruff Settings ------------------------------------------------------------
 [tool.ruff]
-target-version = "py38"
+target-version = "py39"
 src = ["nutree", "tests"]
 
 [tool.ruff.lint]
diff --git a/tests/fixture.py b/tests/fixture.py
index 3ef055c..d347df9 100644
--- a/tests/fixture.py
+++ b/tests/fixture.py
@@ -15,7 +15,7 @@
 import uuid
 from random import randint
 from textwrap import dedent, indent
-from typing import IO, Any, List
+from typing import IO, Any
 
 from nutree.common import ReprArgType
 from nutree.tree import Node, Tree
@@ -233,7 +233,7 @@ def create_typed_tree_simple(
     return tree
 
 
-def generate_tree(level_defs: List[int]) -> Tree:
+def generate_tree(level_defs: list[int]) -> Tree:
     """Generate a tree.
 
     Example:
diff --git a/tests/test_serialize.py b/tests/test_serialize.py
index 53aec5c..e919281 100644
--- a/tests/test_serialize.py
+++ b/tests/test_serialize.py
@@ -11,7 +11,7 @@
 import pprint
 import tempfile
 import zipfile
-from typing import Any, Tuple
+from typing import Any
 
 import pytest
 from nutree import Node, Tree
@@ -21,7 +21,7 @@
 from . import fixture
 
 
-def _get_fp_result(fp, *, do_print=True, assert_len: int) -> Tuple[str, dict]:
+def _get_fp_result(fp, *, do_print=True, assert_len: int) -> tuple[str, dict]:
     fp.seek(0)
     text = fp.read()
     data = json.loads(text)
diff --git a/tests/test_typing_concept.py b/tests/test_typing_concept.py
index b8c0812..908e9b8 100644
--- a/tests/test_typing_concept.py
+++ b/tests/test_typing_concept.py
@@ -6,7 +6,7 @@
 
 from __future__ import annotations
 
-from typing import Generic, List, Type, cast
+from typing import Generic, cast
 from uuid import UUID, uuid4
 
 from typing_extensions import Any, Self, TypeVar, reveal_type
@@ -19,7 +19,7 @@ class Node(Generic[TData]):
     def __init__(self, data: TData, parent: Self):
         self.data: TData = data
         self.parent: Self = parent
-        self.children: List[Self] = []
+        self.children: list[Self] = []
 
     def add(self, data: TData) -> Self:
         node = self.__class__(data, self)
@@ -28,7 +28,7 @@ def add(self, data: TData) -> Self:
 
 
 class Tree(Generic[TData, TNode]):
-    node_factory: Type[TNode] = cast(Type[TNode], Node)
+    node_factory: type[TNode] = cast(type[TNode], Node)
 
     def __init__(self):
         self._root: Node = self.node_factory("__root__", None)  # type: ignore