Abstract: Autophagy is a highly conserved process in eukaryotes in which the cytoplasm, including excess or aberrant organelles, is sequestered into double-membrane vesicles and delivered to the degradative organelle, the lysosome/vacuole, for breakdown and eventual recycling of the resulting macromolecules. This process has an important role in various biological events such as adaptation to changing environmental conditions, cellular remodeling during development and differentiation, and determination of lifespan. Auto-phagy is also involved in preventing certain types of disease, although it may contribute to some pathologies. Recent studies have identified many components that are required to drive this complicated cellular process. Auto-phagy-related genes were first identified in yeast, but homologs are found in all eukaryotes. Analyses in a range of model systems have provided huge advances toward understanding the molecular basis of autophagy. Here we review our current knowledge on the machinery and molecular mechanism of autophagy.