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. Complex actions such as gene expression and signal transduction control differentiation process. Rat Preadipocytes are present throughout adult life in adipose tissue and can proliferate and differentiate into mature adipocytes. They contribute to increased adipose tissue mass. In vitro studies indicate that various tissue-derived preadipocytes exhibit different lipid accumulations, adipogenic transcription factor expression, and TNFα-induced apoptosis. There is also a close relationship between adipocyte differentiation and many physiological and pathological processes including fat metabolism, obesity, diabetes, hyperlipidemia, and breast cancer.