It turns out that retinoic acid and the enzyme CYP26B1 are heavily involved in regrowing missing limbs, determining what goes where before forming new tissue. Future technology inspired by axolotls could possibly help humans regenerate limbs—we have what is needed, but need to find out how to make those pieces communicate like they do in axolotls. Larger limbs at proximal sites closer to the body, such as arms, contain more retinoic acid and less CYP26B1 (which breaks the retinoic acid down). And in smaller sites further from the body, like hands, there is less retinoic acid and more CYP26B1. This helps generate fibroblasts, which are connective tissue cells in humans, but regenerative cells in these creatures.