 fuelled by the obesity epidemic , there is considerable interest in the developmental origins of white adipose tissue ( wat ) and the stem / progenitor cells from which it arises . 
 while increased visceral fat mass is associated with metabolic dysfunction , increased subcutaneous wat is protective . 
 there are 6 visceral fat depots : perirenal , gonadal , epicardial , retroperitoneal , omental and mesenteric and it is a subject of much debate whether these have common developmental origins and whether this differs from subcutaneous wat . here 
 we show that all 6 visceral wat depots receive a significant contribution from cells expressing wt1 late in gestation . 
 conversely , no subcutaneous wat or brown adipose tissue ( bat ) arises from wt1 expressing cells . 
 postnatally , a subset of visceral wat continues to arise from wt1 expressing cells , consistent with the finding that wt1 marks a proportion of cell populations enriched in wat progenitors . 
 we show all visceral fat depots have a mesothelial layer like the visceral organs with which they are associated and provide several lines of evidence that wt1 expressing mesothelium can produce adipocytes . 
 these results : reveal a major ontogenetic difference between visceral and subcutaneous wat ; pinpoint the lateral plate mesoderm as a major source of visceral wat ; support the notion that visceral wat progenitors are heterogeneous ; and suggest that mesothelium is a source of adipocytes . 
Supplementary Material