Yoshinori Ohsumi's research in the 1990s using yeast cells was pivotal in advancing the understanding of autophagy. He discovered 15 genes essential for autophagy by observing the accumulation of autophagosomes when he disrupted protein degradation pathways in starved yeast cells. Ohsumi's work led to the 2016 Nobel Prize in Physiology or Medicine and demonstrated that autophagy is a normal process in cells for degrading and recycling components. Autophagy is important for many cellular functions and diseases, playing both protective and pathological roles in conditions like cancer, neurodegeneration, and infection.