Yoshinori Ohsumi, at the University of Tokyo, resolves the main obstacle that had kept the study of autophagy stalled for two decades: yeast cells are too small to distinguish their internal structures under the microscope, and their vacuoles degrade captured material so quickly that autophagosomes are invisible. Ohsumi designs a mutant yeast strain (Saccharomyces cerevisiae) deficient in vacuolar proteases A, B, and carboxypeptidase Y. When these mutant cells are deprived of nutrients, autophagic bodies accumulate without being degraded, becoming visible for the first time under conventional light microscopy. The result is published in 1992 (Takeshige, Baba, Tsuboi, Noda, and Ohsumi — Ohsumi as senior author and lab director, not first author). With this working visual system, Ohsumi's lab performs the following year a massive genetic screen of autophagy-defective mutants, identifying the first 15 essential genes of the process (Tsukada and Ohsumi, 1993), initially called APG and now known as ATG. This combined work transformed autophagy from a vague morphological observation into a precise molecular discipline, and earned Ohsumi the Nobel Prize in Physiology or Medicine in 2016, as sole laureate.