A strange thing happens to nearly everybody. At night, people turn off the lights, pull up the covers and close their eyes. Six or seven sleeping hours later, they wake up again. Strange, isn't it?
Sleep ①puzzlesscience. Scientists and doctors would rather talk about why one can't fall asleep. They are not sure what causes sleep. The best conditions for sleep are good health and meal neither too big nor too small. No worries and a comfortable place are important, too.
Strange things happen during sleep. For example, you move often. You would feel tired if you didn't. You also dream. Part of your brain is still awake when you sleep. Dreaming happens when the memory and imagination in parts of your brain are still awake. Experiments have shown most of us dream in color. Bad dreams may be caused by stomachache. Don't worry if you dream. Some great stories and poems were begun while their writers slept.
