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Curious about what goes on in your brain when it’s out to dreamland? We can’t blame you.

Experts still have plenty to learn about sleep, but they do know it happens in a cycle, with different things occurring at different stages.

Though you might sometimes wake up feeling as if you dreamed all night long, you don’t necessarily dream during every stage of sleep. Rather, dreams seem to happen mostly during the REM stage of sleep.

Keep reading to explore how and when your dreams float in while you’re fast asleep.

Sleep happens in two main stages. There’s rapid eye movement (REM) sleep and non-rapid eye movement (NREM) sleep. Experts have further split NREM into three distinct substages: N1, N2, and N3.

When you sleep, you cycle through all stages of NREM and REM sleep several times. Deeper, longer REM sleep usually happens near the morning.

Here’s what goes on during these periods of sleep.

NREM Stage N1

You can consider this stage the “falling asleep” stage.

This first and lightest stage of sleep involves:

  • slower heartbeat and breathing
  • slow, rolling eye movements
  • relaxing muscles

You might wake up easily, often without knowing you had already fallen asleep.

NREM Stage N2

Next is the “light sleep” stage, the one you enter before reaching deep sleep.

This stage involves:

  • a drop in body temperature
  • even slower breathing and heartbeat
  • unmoving eyes

You’ll spend most of your time asleep in this stage. While you may not wake up quite so easily as you might during N1 sleep, it’s still fairly easy to be woken up during this sleep stage.

NREM Stage N3

Welcome to your deepest sleep state.

Slow-wave sleep involves:

  • very slow breathing and heartbeat
  • completely relaxed muscles
  • unmoving eyes
  • brain and body processes important for health and well-being, like tissue repair and memory consolidation

You won’t wake easily from this stage of sleep.

REM Stage R

This stage of sleep is where dreams happen. You can think of Stage R as the BOGO sleep stage, since it involves two separate phases:

  • phasic REM sleep, during which your eyes will move rapidly in short bursts
  • tonic REM sleep, which doesn’t involve these eye movements

The REM stage also involves an increase in brain activity, breathing, and heart rate.

To sum up, NREM sleep comes first and involves three stages.

During the final stage of NREM sleep, you’ll get deep, restorative sleep while your brain works, strengthening your immune system, repairing muscles, regenerating cells, and performing other key functions.

During REM sleep, which generally begins about an hour to 90 minutes after you fall asleep, you’ll dream — though you may not remember those dreams.

Both types of sleep are important.

While experts used to believe REM sleep played the most important role in learning and memory processes, they now consider NREM sleep even more important for these functions. Plus, the most restful phase of sleep also happens during NREM sleep.

In the REM stage of sleep, your breathing will speed up slightly, and you’ll experience temporary paralysis as you begin to dream.

Experts don’t fully know why this paralysis happens, but some have theorized your muscles “freeze” so you don’t get up and begin moving around in an unconscious reflection of your dream.

As for how long your dreams last?

Experts aren’t entirely certain, but they do know people typically spend somewhere around 2 hours dreaming every night. You probably won’t remember every single one of those dreams, though.

If someone wakes you up during REM sleep, you might know you were just dreaming, perhaps vividly.

When someone wakes you up during NREM sleep, on the other hand, you’re far less likely to feel as if you were just dreaming.

Can you ever dream during non-REM sleep?

Dreams can happen during any stage of sleep, but the vivid ones that you remember tend to happen during REM sleep.

A small 2016 study used something called a TMS-EEG — a device that combines transcranial magnetic stimulation (TMS) and an electroencephalogram (EEG) test to look at brain activity — to explore whether people waking from restful NREM sleep reported dreams.

Over half the participants reported having dreams when woken from NREM sleep. The researchers did note that their descriptions of the dream experiences tended to be both shorter and less detailed than descriptions of REM dream experiences.

The longer the story a participant told about their dream, the more likely their EEG was to show brain waves resembling those of awake people — like brain wave patterns during REM sleep.

It’s not uncommon to want to get rid of nightmares, have more interesting dreams, or control what happens during your dreams.

Unfortunately, you can’t always pop out of a nightmare or snooze-worthy dream (pun intended) as easily as you might wish. Still, during REM sleep, you could have some level of consciousness of the fact that you’re dreaming.

About 55 percent of people will have this type of dream, called a lucid dream, at least once in their life.

During a lucid dream, you can change or control the content of your dream since you know it is, in fact, a dream.

Try these tips if you want to try to increase your awareness when dreaming:

  • Wake back to bed method (WBTB). As the name of this approach implies, you wake up shortly after going to sleep. For example, you can set an alarm for 5 hours post-bedtime and fall asleep like you usually would. After your alarm goes off, stay awake for about 30 minutes doing a calm activity that keeps you alert, like reading. Go back to sleep after that period and you may experience a lucid dream.
  • Dream journaling. Tracking your dreams helps you remember them. This may make it easier for you to recognize when you’re dreaming. It’s a good idea to jot down your dreams right after you wake up, then read your dream journal over, especially before bedtime.
  • Mnemonic induction of lucid dreams (MILD). With this method, you set an intention for yourself ahead of time to remember that you’re dreaming. You can do this by repeating this intention out loud to yourself.

Learn more about lucid dreaming.

Wake yourself up

Maybe you find yourself in a lucid dream but you’d really prefer to wake up.

To encourage wakefulness and move on, try:

  • going to sleep in the dream
  • blinking or speaking out loud
  • reading in your dream (this can help you leave the REM stage)

A note on lucid dreaming

Lucid dream-like experiences can happen with sleep paralysis, short episodes where you lose muscle function while waking up or shortly after falling asleep.

You might sense a presence in your room or have a hallucination-like experience that feels as if you’re dreaming while awake. Since you can’t move, episodes of sleep paralysis can feel pretty terrifying, but they go away on their own, usually within a couple of minutes.

These tips can help prevent sleep paralysis.

It’s also worth keeping in mind that trying to lucid dream typically involves waking yourself up after you’ve fallen asleep. Once in a while, this may not matter too much. But it can do a number on your sleep schedule if you’re trying to lucid dream on a regular basis.

Sticking to a sleep schedule is a key factor in getting the right amount of sleep for optimal health and function.

The vivid dreams that stick with you into the morning, perhaps even leaving you muttering, “How weird was that?” usually happen during REM sleep — but you can dream during other stages of the sleep cycle, too.

You may not remember your dreams, but you’re still having them. It’s possible they might even help you process information and emotions.

Interested in learning more about common dreams and what they might mean? Find out here.

Breanna Mona is a writer based in Cleveland, Ohio. She holds a master’s degree in media and journalism and writes about health, lifestyle, and entertainment.