Denied of sleep, we find it but impossible to keep our eyes open and our thoughts focused. A new study based on fruit flies may have pin-pointed the origins of this biological lullaby, and with it a deeper understanding of our need for rest on a cellular level.

Researchers from the University of Oxford in the UK have identified our cell's mitochondria as responsible for signaling when the body has to get some shut-eye as soon as possible.

These tiny power generators cause a kind of metabolic overload in sleep-regulating neurons, the researchers suggest, which in simple terms indicates when our brain is running on empty. Through sleep, this overload can be reset, ensuring the brain remains in a healthy state.