Almost all cells are marked by a phenomenon called autophagy, which is degradation of cellular internal components that are no longer able to exert their functions. Autophagy requires engagement of lysosomal hydrolytic enzymes. It captures waste protein aggregates, used or damaged organelles (for example, mitochondria, as in the image), and excessively produced secretory proteins (crinophagy). First, the objects to be disintegrated are surrounded by double membranes derived from the endoplasmic reticulum. Then, the autophagosome fuses with enzyme-containing lysosomes. Internal cellular structures are disintegrated there to simple molecules (sugars, amino acids, and fats) by the enzymes, and the resulting substances are then transported into the cytoplasm to be recycled.

The image also depicts some intact mitochondria #1 and #2, a lipid droplet, large clathrin-coated vesicles #1 and #2, as well as some smaller membrane vesicles, and a fragment of the cell nucleus in the cell cytoplasm.