Sleep / Interactive

A map of one night: the stages of sleep

Sleep is not one single stretch. It is made of cycles that repeat several times through the night. Move over the chart below and see what each moment is.

An example night, from 23:00 to 07:00. It does not belong to a real person; it was drawn to resemble a typical adult night.

Move over the chart or tap it. With the keyboard, the Tab key moves between sections, and the left and right arrows go to the previous or next section.

Stages

In sleep studies, the stages are told apart by brain waves and eye movements. Non-REM sleep has three stages: N1, N2, N3. REM sleep is added to these.¹

Awake: You may wake briefly between two cycles.¹
N1: The transition from wakefulness to sleep. It usually lasts a few minutes.²
N2: You are now asleep; sleep is light. The largest part of the night is spent in this stage.²
N3: Deep sleep, or slow wave sleep. It lasts longer in the first half of the night.^1,2
REM: The eyes move quickly and the brain is as active as when awake. Most dreams happen in this stage; the muscles relax and the arms and legs stay still for a while. REM periods get longer towards morning.^1,2

Cycles

A cycle starts with non-REM sleep and ends with REM. The cycle starts again every 80 to 100 minutes; there are usually 4 to 6 cycles in a night.¹ The first REM comes about 90 minutes after falling asleep.² This is why the start of the night leans towards deep sleep and the end towards REM sleep.

Time spent in each stage in this example night
Stage	Minutes	Share

These proportions change with age. In adults, the share of deep sleep and REM falls with age, and the share of N1 and N2 rises.⁴

For expertsAASM terminology, scoring

In 2007 the AASM visual scoring task force reorganised the Rechtschaffen and Kales (1968) stages: N1, N2, N3 and R. Because there was no evidence to justify splitting slow wave sleep into two stages, the old stages 3 and 4 were merged under N3. Scoring continues in 30-second epochs; attenuation of the alpha rhythm was accepted as the most valid electrophysiological marker of sleep onset. Because K complexes and slow waves are most prominent frontally and spindles centrally, three EEG derivations, two EOG and one chin EMG channel were recommended.³

In the 2004 meta-analysis by Ohayon et al. (65 studies, 3,577 people), total sleep time, sleep efficiency, percentage of slow wave sleep, percentage of REM and REM latency fell with age in adults; sleep latency, percentage of N1 and N2, and wake after sleep onset rose.⁴

Sources

National Heart, Lung, and Blood Institute. How Sleep Works: Sleep Phases and Stages. nhlbi.nih.gov/health/sleep/stages-of-sleep · Institutional page, last updated 24.03.2022. Accessed: 18.10.2026.
National Institute of Neurological Disorders and Stroke. Brain Basics: Understanding Sleep. ninds.nih.gov · Institutional page, last reviewed 25.02.2025. Accessed: 18.10.2026.
Silber MH, Ancoli-Israel S, Bonnet MH et al. The visual scoring of sleep in adults. Journal of Clinical Sleep Medicine. 2007;3(2):121-131. doi:10.5664/jcsm.26814 · AASM task force report.
Ohayon MM, Carskadon MA, Guilleminault C, Vitiello MV. Meta-analysis of quantitative sleep parameters from childhood to old age in healthy individuals: developing normative sleep values across the human lifespan. Sleep. 2004;27(7):1255-1273. doi:10.1093/sleep/27.7.1255 · Meta-analysis.