In this section, we describe about key upstream factors to lead to the activation, differentiation of skeletal muscle cells in the mouse and chick models, such as Pax3/Pax7 genes. They are involved in gene regulatory networks at various sites of skeletal muscle formation. And microRNAs intervene with emerging evidences for novel roles to regulate key factors in myogenesis. We discuss new myogenic insights into mechanisms underlying the transcriptional activity of these factors.