Autophagy, or cellular self-eating, is a cellular pathway involving the engulfment of intracellular organelles or pathogens, leading to protein and organelle degradation, elimination of pathogens or energy recycling. The two important steps of autophagy, the discovery of autophagosome formation and organelle degradation in lysosome, have won the 2016 and 1974 Nobel Prize in Physiology or Medicine, respectively, which indicates the great significance of autophagy. The primordial and vital function of autophagy is preserved in all eukaryotic organisms, from yeast to humans. Autophagic dysfunction can result in diverse pathological changes, and is closely associated with microbial infection, cancer, neurodegeneration and ischemic diseases. Moreover, autophagy plays complicated and even divergent roles in different types of diseases, cells, conditions and pathological processes.