The brain is the most important organ in the body and without it, life would not exist. Metaphorically, the brain can be considered a master computer. Brain functions include physical behavior, emotions, learning ability and memory. Since the beginning of scientific exploration, the brain has been an important area of ​​interest and its complexity still perplexes scientists today. New research methods and technological advances have allowed humans to understand the brain better in the past 10 years than in previous centuries (Brain Basics, 2013.) Research on the role of sleep in brain functionality is surprising and promising. The quantity and quality of sleep an individual receives affects learning ability and the risk of developing brain diseases such as Alzheimer's disease. Sleep is defined as a period of reduced activity during which an individual's response to their environment is diminished (Healthy Sleep, n.d.). The body experiences fluctuations in brain wave activity, breathing, heart rate, and other functions. These changes occur during two main stages of sleep. Rapid eye movement (REM) sleep is the stage during which dreaming typically occurs and absorption of newly learned information takes place. Deep restorative sleep known as slow-wave sleep consolidates memories (Healthy Sleep, n.d.). Recent studies have shown that some people may not experience the two stages of sleep. This can contribute to problems with learning, memory and brain restoration. A study from the University of Rochester Medical Center investigated the importance of sleep in ridding the brain of cellular waste. The study concludes that during sleep, human brain cells shrink up to 60% of their normal size. Although this can see...... middle of paper ...... Izheimer's disease. "Disease-a-Month 58.12 (2012): 666-676. Print." Healthy Sleep." Healthy Sleep. Np, nd Web, November 11, 2013, from http://healthysleep.med.harvard.edu/healthy/ “How brain and nerve cells change during Alzheimer's disease." BrightFocus Foundation , September 21, 2013. Web 2013, from http://www.brightfocus.org/alzheimers/about/understanding/brain-nerve-cells.html Luscombe, B. (October 17, 2013). (and that's a good thing). -thats-a-good-thing/. Sifferlin, A. (2013, March 12). Two studies find promising new ways to detect Alzheimer's disease earlier. time.com/2013/03/12/two-studies -find-promising-new-ways-to-detect-Alzheimer’s-earlier./