All-trans retinoic acid (ATRA) is a metabolite of vitamin A that plays a crucial role in regulating gene expression and cellular differentiation. It is primarily involved in processes such as embryonic development, vision, and immune function. ATRA binds to specific nuclear receptors, influencing the transcription of genes that are essential for various biological functions. ATRA is also used in medical treatments, particularly for certain types of leukemia, such as acute promyelocytic leukemia (APL). In this context, it helps to induce remission by promoting the differentiation of cancerous cells into more mature forms, thereby improving patient outcomes.