Mitochondria are energy-converting organelles that act as "the power plants of the cell", but also accumulate oxidative stress due to their own by-products, reactive oxygen species during electron transport. Numerous studies suggest that cells employ diverse quality control pathways against oxidative damage, and that defects in these pathways are associated with various human diseases. Our group focuses on "mitophagy", a mechanism that sequesters and eliminates mitochondria as whole organelles. We have recently established a model system to analyze this phenomenon, and identified a key factor that determines the selectivity of mitochondrial degradation. The aim of our study is to expand the current projects, uncovering the molecular basis and general principle of mitophagy, and elucidating the physiological function of this degradation process as an intracellular quality control system.