Objective: Embryonic stem cells (ESC) pluripotency is maintained through a complex interplay of different signaling pathways and a network of transcription factors. Although much is known about this pluripotency selfrenewal circuitry, the molecular events that lead ESC to exit from pluripotency and begin differentiation are currently less known. All-trans retinoic acid (atRA), plays important and pleiotropic roles in embryonic development and ESC differentiation. The objective of the present study is to check the autocrine synthesis of atRA by ESC, test its role in spontaneous differentiation of ESC as embryoid bodies (EBs), and analyze the expression of the enzymes and proteins involved in atRA synthesis pathway.