Myoblasts are progenitor cells or stem cells that are responsible for the formation and repair of skeletal muscle tissue. They are small, post-mitotic cells with only one nucleus and very little cytoplasm. 

Myoblasts are capable of fusion and contractile protein synthesis and have a high capacity for myogenic differentiation. Uni-nucleated myoblasts fuse to form long cylindrical striated skeletal muscles that are multinucleated.