The autophagy-related protein 13 (Atg13) plays an important role in the formation of autophagosomes. Autophagosomes are formed in response to nutrient deprivation and function as the transport vesicles for organelles, proteins, and protein complexes targeted for lysosomes that digest these cargos to produce energy and nutrients. Atg13 is activated by the mTOR pathway and forms a complex with the FIP200 protein. This complex is involved in enhancing the activity of the ULK1 kinase which is required for the formation of autophagosomes. Atg13/FIP200 faciliates the localization of ULK1 to pre-autophagosomes, and subsequently stabilizes ULK1. Autophagy is an important process in development, growth, and cell differentiation, and disruption of this process may contribute to cancer, aging, and neurodegenerative diseases.