AbstractPreadipocyte cellular models have proven to be useful tools for the study of adipose cell development in vitro (1–5). Among these models are preadipocyte clonal lines from various origins and primary cultures of fibroblast-like adipose precursor cells present in the stromal-vascular fraction of adipose tissue, which can be isolated from several depots and various species, including the human (see Chapter 20). The availability of these cellular models has allowed crucial advances with respect to the characterization of the main steps of the differentiation process from the preadipocyte to the adipocyte in (1) delineating the kinetics of expression of adipose specific markers, (2) cloning some of these markers and studying their hormonal control, and (3) giving evidence of new secreted compounds from adipose cells (6–13). In addition, the availability of multipotent or totipotent stem cells (1,14,15) gives the opportunity of approaching the events that govern the process of determination of progenitors to the adipose lineage. These stem cell systems are thus expected to allow characterization of still missing key genes, as well as marker(s) of the unipotent adipoblast before its commitment to a preadipocyte. KeywordsEmbryonic Stem CellRetinoic AcidLeukemia Inhibitory FactorClonal LinePluripotent Embryonic Stem CellThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.