While we sleep we enter a periodic state of rest during which our consciousness of the world is suspended, allowing our bodies to rest up. Our brains have a number of functions, structures and “sleep centers” that regulate the cycle of sleep and wakefulness. At the same time, our bodies produce substances that when released into the blood stream, make us sleepy. When this process is altered –by stress, worries, disorders and physical ailments- we may suffer from insomnia.