Myogenesis is the formation of muscular tissue, in particular during embryonic development.
Muscle fibers form from the fusion of myoblasts (muscle stem cells) into multi-nucleated fibers (called myotubes). In the early development of an embryo these myoblasts will proliferate if enough fibroblast growth factor is present. When the FGF runs out, the myoblasts cease division and secrete fibronectin onto their extracellular matrix.
The second stage involves the alignment of the myoblasts into the myotubes. The identity of the myoblasts in this stage is not crucial. Studies have shown that even rat and chick myoblasts have aligned! 
Myocyte Enhance Factors (MEFs) promote myogenesis.
- YAFFE D, FELDMAN M. THE FORMATION OF HYBRID MULTINUCLEATED MUSCLE FIBERS FROM MYOBLASTS OF DIFFERENT GENETIC ORIGIN.