Reports on the concept of sleep medicine, focusing on the benefits of a good sleep. For a long time, sleep researchers have asked why we sleep and what physiological and mental needs require sleep. Today, we understand that sleep is important for productivity, health, cognition, and well-being. As a consequence, physical recreation, hormone secretion, immune systems, memory functions, and mood are all related to sufficient and restorative sleep. Thus, a good sleep quality is essential. As biomedical engineers, we would like to quantify this ultimate "sleep quality," but how can we assess it? Explores how the quality of sleep can be assessed. © 2010-2012 IEEE.