This issue of Clinics in Plastic Surgery offers the plastic surgeon (and facial plastic surgeon, reconstructive surgeon, burn surgeon, any surgeon working with face or body reconstruction or rejuvenation) an intensive review of all aspects of working with fat. The title succinctly sums it up that clinical applications, currently known concepts, and future expectations of working with fat for reconstructive or cosmetic surgery are presented here.  The Editors and their selected are peerless in the field that focuses on biology of fat, adipose derived stem cells, and growth factors; harvesting, processing, and storage of harvested fat; how to maximize the results of fat grafting; and safety issues with fat grafting and growth factors.  Practical clinical applications, currently known concepts, and future expectations of working with fat for reconstructive or cosmetic surgery are presented here. Because of the depth and comprehensiveness of the material presented by the experts in this field, this issues is presented in two parts; Part 1 topics include: Adipose Tissue and Stem/Progenitor Cells: Discovcery and Development; Cryopreservation of Adipose Tissue and Adipose Derived Stem Cells; Adipose Stem Cells: Biology, Safety, Regulation, and Regenerative Potential; History and Development of Fat Grafting: from Ram Fat to Stem Cells; Condensation of Tissue and Stem Cells for Fat Grafting; Can We STtandardize the Techniques for Fat Grafting;  How Fat Survives and Remodels after Grafting; The Role of Fat Grafting in Facial Rejuvenation; Gluteal Augmentation with Fat Grafting-the "Brazilian Buttock Technique:" 30 Years'' Experience; Fat Grafting for Treatment of Burns, Burn Scars, and other Difficult Wounds.