Adipocytes play an important role in energy storage and metabolism. Adipocyte differentiation is a developmental process that is critical for metabolic homeostasis and nutrient signaling. It is controlled by complex actions involving gene expression and signal transduction. Preadipocytes are present throughout adult life in adipose tissue and can proliferate and differentiate into mature adipocytes according to the energy balance. The proliferation and differentiation of these preadipocytes contribute to increases in adipose tissue mass. In vitro study indicates that different tissue-derived preadipocytes exhibit differently in lipid accumulation, adipogenic transcription factor expression, and TNF?-induced apoptosis. It has also been demonstrated that there is a close relationship between adipocyte differentiation and many physiological and pathological processes including fat metabolism, energy balance, obesity, diabetes, hyperlipidemia and breast cancer. HPA-v from AcceGen Biotech Research Laboratories are isolated from human visceral fat tissue. HPA-v are cryopreserved at primary culture and delivered frozen. Each vial contains >1 x 10^6 cells in 1 ml volume. HPA-v are characterized by immunofluorescent method with antibodies to CD44, CD90 and lipid staining after differentiation. HPA-v are negative for HIV-1, HBV, HCV, mycoplasma, bacteria, yeast and fungi. HPA-v are guaranteed to further culture at the conditions provided by AcceGen Biotech Research Laboratories.