A myoblast's a type of stem cell that exists in muscles.Skeletal muscle fibers are made when myoblasts fuse together; muscle fibers therefore have multiple nuclei. Myoblasts that don't form muscle fibers differentiate into satellite cells. These satellite cells remain adjacent to a muscle fiber, separated only by its cell membrane and by the endomysium (the connective tissue investment that divides the muscle fascicles into individual fibers).… (More on Myoblast)