Adipogenesis in vivo has obvious clinical applications in Plastic and Reconstructive Surgery. Free fat injection is unpredictable. In mice matrigel(mouse sarcoma extracellular matrix) when injected subcutaneously and when combined with bFFG, is spontaneously replaced by fat. We have investigated this process in mice in a chamber model containing a vascular pedicle and found that if the matrigel and FGF are denied direct contact with a fat cell source (this may be free adipose tissue, free muscle or mouse or human BM-MSC's from bone marrow or lipoaspirate)no fat tissue will form. Equally there must be a patent vascular pedicle to promote angiogenesis which appears an essential prelude to adipogenesis. Finally, a non collapsable space appears necessary to permit expansile growth of the adipose tissue. A matrigel equivalent is the major limitaion to be able to apply this clinically.