The sartorius muscle is part of the inner from thigh. It is in fact the longest single muscle of the human body which runs down the full length of your thigh. It's purpose is to assist in flexion of the hip and the knee as well as other minor areas.
Targeting the inner thigh muscle is a great way for men and women to tone this part for a healthier and thinner look. Lunges of most types are quite effective at stimulating this muscle group as well as step-ups.