This section offers an overview on the basic concepts of sleep: how sleep is defined, measured and regulated. While these questions may appear at first glance trivial, they offer a plethora of questions that are under active research and development. The many interview clips offer views from top scientists on their work and thoughts about sleep and sleep research.

REM sleep appears to remain as paradoxical as it was upon its discovery. The profound changes at the level of brain activity as well as their outcomes in the rest of the body have been explored, but the cause for these remarkable changes has remained unknown.

While sleep is often regarded as a phenomenon tightly associated with brain activity, it is evident that the all body function undergo profound modification during sleep, which are different during NREM and REM sleep.

What is the function of sleep is perhaps the most important question in sleep research. Despite vast amount of research, we still cannot give a final answer, and some researchers suggest that the entire question is not relevant.

Sleep is important for healthy brain function, be it cognitive or emotional. Very recent research has emphasized the role of sleep in neural plasticity, particularly in learning and memory, but also in emotional health.

Curtailment of sleep is a common problem in modern societies, be it due to work or social factors. Deprivation of sleep is also a common procedure in sleep research.

Sleep changes throughout the life span, from newborn to old age. Some of the changes are gradual, some more abrupt.

Men and women do not sleep equally – a realization that is slowly developing.

Circadian component in the two-process model of sleep regulation guides the body to sleep at a proper time. Many sleep problems can be alleviated by restoring a proper circadian rhythm.

Many common pharmacological treatments affect vigilance state. However, this side effect is rarely taken in consideration when introducing treatments.