Below is what normal sleep architecture looks like. All stages of sleep are necessary for normal functioning.
A normal sleep architecture would entail all stages of sleep. Normal sleep architecture in an average adult would be as follows:
Stage 1 (5%)
Stage 2 (50%)
Stages 3 and 4 (AKA Deep Sleep: 20-25%)
REM sleep (20-25%)
Sleep latency is defined as the time it takes to fall asleep from Lights Out. Normal Sleep latency is 5-10 minutes.
REM latency is defined as the time it takes to get into REM sleep from Sleep Onset. Normal REM latency is 90-120 minutes. A short REM latency could be indicative of either REM Rebound, depression, sleep deprivation, or even Narcolepsy.