diff --git a/README.md b/README.md
index 72595cc..9a7aeeb 100644
--- a/README.md
+++ b/README.md
@@ -45,8 +45,8 @@ python build.py
 cd ../../
 ```
 
-### Octree Generation Example
-Provide one example data 1A1E, also in refined-set.    
+### Octree Generation Example (Optional)
+Provide one example data 1A1E from refined-set.    
 Following steps can generate the points and build the OctSurf. (Default density for points is 6, and depth for OctSurf is 10.)    
 We also provide python tool to parse the generated OctSurf, and visualize it by generating vtk files that can visualize in Paraview.    
 ```angular2