Adipose tissue is a major metabolic organ, and it has been traditionally 
classified as either white adipose tissue (WAT) or brown adipose tissue (BAT). 
WAT and BAT are characterized by different anatomical locations, morphological 
structures, functions, and regulations. WAT and BAT are both involved in energy 
balance. WAT is mainly involved in the storage and mobilization of energy in the 
form of triglycerides, whereas BAT specializes in dissipating energy as heat 
during cold- or diet-induced thermogenesis. Recently, brown-like adipocytes were 
discovered in WAT. These brown-like adipocytes that appear in WAT are called 
beige or brite adipocytes. Interestingly, these beige/brite cells resemble white 
fat cells in the basal state, but they respond to thermogenic stimuli with 
increased levels of thermogenic genes and increased respiration rates. In 
addition, beige/brite cells have a gene expression pattern distinct from that of 
either white or brown fat cells. The current epidemic of obesity has increased 
the interest in studying adipocyte formation (adipogenesis), especially in 
beige/brite cells. This review summarizes the developmental process of adipose 
tissues that originate from the mesenchymal stem cells and the features of these 
three different types of adipocytes.