diff --git a/CMakeLists.txt b/CMakeLists.txt
index d5dffc2..d93853e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -71,6 +71,7 @@ install(DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/src/cpp/include/
   COMPONENT headers
   FILES_MATCHING PATTERN "*.h*")
 
+
 export(EXPORT cytnx_targets FILE ${CMAKE_CURRENT_BINARY_DIR}/CytnxTargets.cmake NAMESPACE cytnx_core::)
 export(PACKAGE cytnx_core)
 
@@ -80,8 +81,13 @@ export(PACKAGE cytnx_core)
 set(PYBIND11_FINDPYTHON ON)
 find_package(pybind11 CONFIG REQUIRED)
 
-pybind11_add_module(pycytnx MODULE src/cpp/pybind/main.cpp)
-target_link_libraries(pycytnx PUBLIC cytnx_core)
+pybind11_add_module(_core MODULE src/cpp/pybind/main.cpp)
+target_link_libraries(_core PUBLIC cytnx_core)
+
+install(DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/src/cytnx_core
+    DESTINATION ${CMAKE_INSTALL_PREFIX}
+)
+install(TARGETS _core LIBRARY DESTINATION ${CMAKE_INSTALL_PREFIX}/cytnx_core)
 #install(TARGETS pycytnx DESTINATION ${SKBUILD_PROJECT_NAME})
-install(TARGETS pycytnx DESTINATION ${CMAKE_INSTALL_PREFIX}/cytnx_core)
 message(STATUS " skbuild Installation Prefix: ${SKBUILD_PROJECT_NAME}")
+message(STATUS " skbuild Installation Prefix: ${SKBUILD_HEADERS_DIR}")
diff --git a/README.md b/README.md
index 84b6a64..2286d8d 100644
--- a/README.md
+++ b/README.md
@@ -34,3 +34,12 @@ Running pytest:
 - cmake 3.15+ (see CMakeList.txt, default 3.20)
 
 * most of the deps should be able to install via pypi.
+
+
+## Compile directly the C++ package
+
+```bash
+   $mkdir build
+   $cd build
+   $cmake ../ -DCMAKE_INSTALL_PREFIX=<install destination>
+```
diff --git a/pyproject.toml b/pyproject.toml
index 956df6e..d0c3dd3 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -12,6 +12,7 @@ dependencies = []
 [tool.scikit-build]
 minimum-version = "build-system.requires"
 build-dir = "build/{wheel_tag}"
+build.tool-args = ["-j4"]
 
 [tool.black]
 line-length = 88
diff --git a/src/cpp/include/test.hpp b/src/cpp/include/cytnx_core/test.hpp
similarity index 52%
rename from src/cpp/include/test.hpp
rename to src/cpp/include/cytnx_core/test.hpp
index e8345bc..de09796 100644
--- a/src/cpp/include/test.hpp
+++ b/src/cpp/include/cytnx_core/test.hpp
@@ -1,9 +1,9 @@
 #pragma once
 
-#include <cstring>
+#include <string>
 
 namespace cytnx_core {
 
-void test();
+std::string test();
 
 }
diff --git a/src/cpp/pybind/main.cpp b/src/cpp/pybind/main.cpp
index 9a57ecd..de76e29 100644
--- a/src/cpp/pybind/main.cpp
+++ b/src/cpp/pybind/main.cpp
@@ -1,10 +1,12 @@
+#include <cytnx_core/test.hpp>
 #include <pybind11/pybind11.h>
+#include <string>
 
-std::string hello_from_bin() { return "Hello from Kai!"; }
+std::string hello_from_bin() { return cytnx_core::test(); }
 
 namespace py = pybind11;
 
-PYBIND11_MODULE(pycytnx, m) {
+PYBIND11_MODULE(_core, m) {
   m.doc() = "pybind11 hello module";
 
   m.def("hello_from_bin", &hello_from_bin, R"pbdoc(
diff --git a/src/cpp/src/CMakeLists.txt b/src/cpp/src/CMakeLists.txt
index 7c96618..762a393 100644
--- a/src/cpp/src/CMakeLists.txt
+++ b/src/cpp/src/CMakeLists.txt
@@ -1,6 +1,5 @@
 target_sources_local(cytnx_core
   PRIVATE
-
   # put cpp files here
   test.cpp
 
diff --git a/src/cpp/src/test.cpp b/src/cpp/src/test.cpp
index c3e8fcb..5167bb1 100644
--- a/src/cpp/src/test.cpp
+++ b/src/cpp/src/test.cpp
@@ -1,4 +1,7 @@
-#include "test.hpp"
+#include <cytnx_core/test.hpp>
 #include <iostream>
+#include <string>
 
-void test() { std::cout << "Hello from test" << std::endl; }
+namespace cytnx_core {
+std::string test() { return "Hello from test"; }
+} // namespace cytnx_core
diff --git a/src/cytnx_core/__init__.py b/src/cytnx_core/__init__.py
index b919c0f..e581d39 100644
--- a/src/cytnx_core/__init__.py
+++ b/src/cytnx_core/__init__.py
@@ -1,4 +1,4 @@
-from cytnx_core.pycytnx import hello_from_bin
+from cytnx_core._core import hello_from_bin
 
 
 def hello() -> str: