The primary role for RIP140 in fat is to repress brown fat genes in white fat depots. Thus, RIP140 blocks the expression of the BRITE (Brown-in-White) program in white adipose tissues to maintain the integrity of this energy storage depot. Adipose tissues constitute a remarkably dynamic organ that responds to stimuli ranging from nutrients and hormones to external temperature. Brown and white adipose tissues (BAT and WAT) differ in their appearance and function due to distinct gene expression profiles. The transcriptional coregulator RIP140, encoded by the NRIP1 gene, is present in adipose tissues and enables white and brown adipocytes to express unique sets of genes that determine their very different functions. Genetically modified mice that lack the NRIP1 gene are lean and resistant to diet-induced obesity. Although RIP140 is detected in both brown and white adipose depots it has different roles in each tissue. RIP140-null white adipocytes show profound alterations in the transcriptome in contrast to brown adipocytes that display few changes in gene expression. The function of RIP140 as a transcriptional corepressor correlates with the elevated expression of many genes when ablated in white adipocytes. In WAT, it represses genes normally expressed at high levels in BAT, including UCP1, CIDEA, FABP3, PPARα, L-PGDS and Gyk. In wild type mice, under conditions of cold exposure, these genes are switched on in BRITE adipocytes within WAT depots. Interestingly, discrete WAT depots show differential responses to cold with subcutaneous being most responsive and visceral mesenteric being largely unresponsive. RIP140 also represses genes associated with early events in brown and BRITE adipocyte differentiation including PRDM16, Tbx1, CD137 and Tmem26. Whereas WAT store lipids that are released into the circulation when required, BAT uses its stored fat to generate heat by oxidation of fatty acids to maintain body temperature. These functions are reflected in tissue morphology, as white adipocytes usually contain a single giant lipid droplet (LD) occupying most of the cytoplasm (unilocular), while brown adipocytes are filled with many smaller LDs (multilocular). Smaller LDs, with higher surface/volume ratio, facilitate the release of stored lipids given the extensive surface accessible to lipases. LD-associated proteins regulate the storage and release of triacylglycerol from LDs and are generally more highly expressed in BAT compared to WAT. The RIP140-regulated gene CIDEA is an important regulator of LD dynamics that is cold-induced in WAT depots. The CIDEA protein coats the surface of the droplets and facilitates their enlargement by lipid transference between adjacent LDs. With the use of specific deletions and point mutations, we have refined its mechanism of action and determined the discrete protein regions involved in each step: LD targeting, dimerization, LD clustering and lipid transference. Thus, RIP140, by repressing genes required for BAT differentiation and function, is important for preventing the inappropriate expression of the BRITE phenotype in WAT depots and represents a valuable target for the activation brown adipocytes in white fat.