All-trans retinoic acid (ATRA) is a metabolite of vitamin A, essential for various biological processes in the body. It plays a crucial role in cell growth, differentiation, and development, particularly in the skin and eyes. ATRA is also involved in regulating gene expression, influencing how cells respond to their environment. In medicine, ATRA is primarily used in the treatment of certain types of leukemia, such as acute promyelocytic leukemia (APL). It works by promoting the differentiation of cancer cells, helping to restore normal blood cell production. ATRA is often combined with other therapies to enhance treatment effectiveness.