diff --git a/heparchy/__init__.py b/heparchy/__init__.py
index abb2b31..5895ba0 100644
--- a/heparchy/__init__.py
+++ b/heparchy/__init__.py
@@ -23,6 +23,20 @@ def open_file(
     ...
 
 
+@ty.overload
+def open_file(
+    path: ty.Union[str, Path], mode: ty.Literal["r"], process: None
+) -> ty.ContextManager[read.hdf.HdfReader]:
+    ...
+
+
+@ty.overload
+def open_file(
+    path: ty.Union[str, Path], mode: ty.Literal["r"], process: str
+) -> ty.ContextManager[read.hdf.HdfProcessReader]:
+    ...
+
+
 @ty.overload
 def open_file(
     path: ty.Union[str, Path], mode: ty.Literal["w"]
@@ -30,8 +44,26 @@ def open_file(
     ...
 
 
+@ty.overload
+def open_file(
+    path: ty.Union[str, Path], mode: ty.Literal["w"], process: None
+) -> ty.ContextManager[write.hdf.HdfWriter]:
+    ...
+
+
+@ty.overload
+def open_file(
+    path: ty.Union[str, Path], mode: ty.Literal["w"], process: str
+) -> ty.ContextManager[write.hdf.HdfProcessWriter]:
+    ...
+
+
 @ctx.contextmanager
-def open_file(path: ty.Union[str, Path], mode: ty.Literal["r", "w"]):
+def open_file(
+    path: ty.Union[str, Path],
+    mode: ty.Literal["r", "w"],
+    process: ty.Optional[str] = None,
+):
     """High level file manager for reading and writing HEP data to HDF5.
 
     Parameters
@@ -40,10 +72,13 @@ def open_file(path: ty.Union[str, Path], mode: ty.Literal["r", "w"]):
         Path on disk where the file is to be opened.
     mode : {'r', 'w'}
         Whether to open the file in 'r' (read) or 'w' (write) mode.
+    process : str, optional
+        If provided, will provide the handler to the process indexed
+        with the value.
 
     Yields
     ------
-    HdfReader or HdfWriter
+    HdfReader or HdfProcessReader or HdfWriter or HdfProcessWriter
         Heparchy's file handler for accessing the HDF5 file.
     """
     if mode not in {"r", "w"}:
@@ -51,9 +86,17 @@ def open_file(path: ty.Union[str, Path], mode: ty.Literal["r", "w"]):
     stack = ctx.ExitStack()
     if mode == "r":
         f = stack.enter_context(read.hdf.HdfReader(path))
+        if process is not None:
+            f = f[process]
     elif mode == "w":
         f = stack.enter_context(write.hdf.HdfWriter(path))
+        if process is not None:
+            f = stack.enter_context(f.new_process(process))
     try:
         yield f
     finally:
         stack.close()
+
+
+with open_file("/scratch/jlc1n20/graftnet/data/h_bb.hdf5", "w", "test") as f:
+    f