We spend a third of our life doing it, but we still don’t know exactly why. Sleep uncovers the mystery, benefits, and difficulties of getting some shut eye. Some highlights include: How does sleeping help the brain? What is the difference between deep-wave sleep and REM sleep, and what causes insomnia? Please note that this product is an authorized edition published by the Meredith Corporation and sold by Amazon. This edition is printed using a high quality matte interior paper and printed on demand for immediate fulfillment.