When do dreams occur?

[Insomniac]

In what stage of sleep do dreams occur? Is it just in REM sleep or in NREM as well?

[Starlight]

'Though dreaming most commonly occurs during the rapid eye movement sleep stage based on there being more dream recall and vividness,[9] dreaming can also occur during NREM sleep.

Research has also shown that dreams during the NREM stage most commonly occur during the morning hours which is also the time period with the highest occurrence of REM sleep. This was found through a study involving subjects taking naps over specific intervals of time and being forcefully awakened, their sleep was separated into naps including only REM sleep and only NREM sleep using polysomnography. This implies that the polysomnographic occurrence of REM sleep is not required for dreaming. Rather, the actual mechanisms that create REM sleep cause changes to ones' sleep experience. Through these changes, by morning, a sub-cortical activation occurs during NREM that is comparable to the type that occurs during REM. It is this sub-cortical activation that results in dreaming during the NREM stage during the morning hours.'

http://en.wikipedia.org/wiki/Non-rapid_eye_movement_sleep#Dreaming_during_NREM

[emilyhobbes]

We say it's about 80% of dreams occur in REM sleep and 20% in NREM

[Insomniac]

We say it's about 80% of dreams occur in REM sleep and 20% in NREM

Is it usually NREM stage 4? And in what stage do we remember dreams?

[zvezda]

approx. 90% dreams tend to occur in REM sleep and these are the dreams that we are most likely to remember. Dreams can occur in NREM stage 4  (remaining 10%) however these dreams tend to be less vivid, shorter in duration and are unlikely to be remembered.