Hi @Yi Yu, I spent a lot of time looking through these, and they are really nice! Here are some things that might help: - I like to lightly indicate the It band, to make sure that the muscle fibers are going to the right spot. In your second image, first drawing, the gluteus maximus is a little small. I think this is because of how you placed the great trochanter and It band. - The fat of a butt hangs down past the muscle fiber. Eventhough the fat with it´s gluteal fold defines the boarder of the form, I like to lightly indicate the actual muscle as well, just to make sure that everythings going to right spot and to train my anatomy X-ray vision I hope this helps :)