While vitamin A is best known for its vital role in vision, this vitamin also participates in physiological activities related to the immune system, maintenance of epithelial and mucosal tissues, growth, reproduction, and bone development. In food, vitamin A typically occurs as a fat compound called retinyl palmitate. The body converts retinyl palmitate to three metabolically active forms of the vitamin: retinol, retinal, and retinoic acid. Bobby had CIS13 retinoic acid as part of his NHS treatment to turn neuroblastomas cells back to healthy cells. It was given in two weeks on, two weeks off pulse doses.