This document describes the muscles of the sole of the foot organized into four layers. The first layer includes the abductor hallucis, flexor digitorum brevis, and abductor digiti minimi muscles. The second layer contains the quadratus plantae and lumbrical muscles. The third layer is made up of the flexor hallucis brevis, adductor hallucis, and flexor digiti minimi brevis muscles. The fourth and final layer comprises the dorsal and plantar interossei muscles. Each muscle is described in terms of its origin, insertion, innervation, and function.