Cover legend: Overlay plots of T1-weighted magnetic resonance images and topographical maps of relative sleep electroencephalography (EEG) power distribution. Rows represent different age groups (from top down: 5–8, 8–11, 11–14, 14–17, and 17–20 years), and columns illustrate the classical frequency bands of the sleep EEG (from left to right: delta, 1–4.5 Hz; theta, 4.75–7.75 Hz; alpha, 8–9.75 Hz; and sigma, 10–15 Hz). Colored crosses surrounding the brain illustrate the digitized electrode positions on the scalp. Nets of high electrode density (128 channels) were used to assess the sleep EEG. EEG power is color coded: Reddish coloring refers to power maxima, and bluish regions indicate power minima; values in between electrodes were interpolated. For more information, see the article by Kurth et al. in this issue (pages 13211–13219).