Historically, white and brown adipocytes were thought to derive from the same precursor cell. However, brown adipocytes instead share a common MYF5/PAX7-positive precursor with muscle cells (Box 1). The MYF5/PAX7-positive precursor is driven to brown adipocyte terminal differentiation by PPARγ and C/EBPs cooperating with the transcriptional co-regulator PRDM16. By contrast, PRDM16 does not affect white adipogenesis. White adipocytes can also be stimulated to display characteristics of brown adipocytes by cold exposure, β-adrenergic signalling, and thiazolidinediones, which appear to function via the indicated factors.