Under good conditions, C. elegans enters and exits four larval stages before becoming a fertile adult. Each developmental stage is punctuated with a molt that entails the shedding of the larval cuticle and the generation of a completely new one. It has been shown that each cuticle is unique in its composition. Molting is a carefully timed process that needs to be coordinated with development, new cuticle synthesis, and cuticle shedding. Mutations in a set of genes called heterochronic genes regulates the timing development and the molts and result in precocious or retarded development of parts of the animals that aren't synchronized with the the animals' life stage.