Sleep problems are extremely common in young children, and the stress that chronic sleep deprivation may impose on parents can be very great. However, the majority of these children will grow out of their sleep problem with no long-term ill effects. Children dream extensively during rapid-eye-movement sleep, and nightmares are common in primary school children. It is also important to note that all small children wake during the night, but usually settle themselves back to sleep, so their parents are unaware that they have woken. Children who are suffering from nightmares will cry out or wake and be obviously frightened. They will remember parts of the nightmare, and can often describe the dream to their parents, either at the time or the following morning. Sleep-walking occurs at a similar stage of sleep to night terrors. It is common, particularly in school-age children, and there is often a family history.