Major aspects of the biology of muscle satellite cells are reviewed: the identification, origin in early development, mechanisms of self-renewal mediated by asymmetric divisions, content in different muscle types and in different ontogenetic stages, role of control genes of the Pax family (in particular, Pax7) and their products in proliferation control, and involvement of growth factors (HGF, FGF, IDF, and TGF-beta) in the activation of these cells after muscle damage. The characteristics of the early stages of myogenic differentiation of activated satellite cells along the pathway similar to muscle formation in embryonic development are discussed.