Mystery of sleep solved A groundbreaking study from the University of Oxford has uncovered a biological trigger for sleep: stress inside mitochondria (the energy producing structures within brain cells). Researchers found that when mitochondria in specialized sleep regulating neurons become overloaded, they leak electrons, producing reactive oxygen species that can damage cells. This leakage acts as a signal to initiate sleep, allowing the brain to reset before damage accumulates. Key findings: 1. Electron leak serves as an internal alarm system for sleep. 2. Sleep is triggered when stress in mitochondria crosses a threshold. 3. Scientists could control sleep in fruit flies by manipulating mitochondrial energy flow. 4. The system works even when powered by light instead of natural electrons. This discovery may explain: 1. The link between sleep, metabolism, and aging. 2. Why small animals sleep more and live shorter lives. 3. Why people with mitochondrial disorders suffer extreme fatigue. Research offers a major insight into why we sleep, connecting it directly to cellular energy metabolism.