When you go to sleep each night, your mind goes on a sort of sleep roller coaster. As you sleep, your brain passes through different sleep stages again and again.

Over the course of a typical night, your brain cycles back and forth through the various stages of sleep four to five times!

Most dreaming occurs during the stage of deepest sleep, called “Rapid Eye Movement” or “REM.” During REM, our eyes begin to move around quickly under our eyelids.

If you have ever watched people sleeping (even family pets!), then you may have noticed their twitching eyelids. This is a perfectly normal part of REM sleep.

Researchers used to believe that people dreamed only during REM, but most experts now agree that dreams can occur at any time during the sleep cycle.

So why do we dream? For centuries, humans have wondered about the meaning and purpose of dreams.

Despite improvements in medical technology and sleep research, experts today still have not reached a conclusion about why people dream. They have, however, developed some interesting theories.

Some experts believe dreams are a way to process all the events and emotions we experience throughout the day. They believe dreams play an important role in our physical, mental and emotional health.

Similarly, other experts claim dreams are a form of problem-solving. They believe our dreams provide us with a safe place to work through problems, questions and dilemmas in our lives.

Other researchers claim dreams are simply a bodily function, much like blinking or burping. Researchers may not be able to agree on why we dream, but they can all agree on one thing: We all do it.

It’s probably a good thing that we dream since we spend a lot of time asleep. Though we may not call it a hobby, we sleep about one-third of our lives. On average, most people sleep about eight hours per night.

When you do the math, you find that most humans sleep approximately 122 days out of every year. By the time you’re 75 years old, you will have spent about 25 years asleep!