Stage 1: light sleep, easily woke, Alpha, slow, rhythmic
Stage 2: Theta, sleep spindles, sudden bursts of activity
Stage 3: Delta, slower, deeper, difficult to wake
Stage 4: Delta, deepest stages, growth hormones released, sleep walk/talk
Stage 5: R.E.M, body paralysed, brain activity speeds up, dreams, Alpha and Beta, replenish brain, recovery