Understanding the stages of sleep

Your brain moves through four distinct sleep stages every night

Each stage plays a key role in memory, repair, restoration, and other key biological functions. The full cycle generally proceeds from light sleep and deep rest into vivid REM dreaming, which repeats between three and five times nightly.

A deeper walk through of the four stages of sleep

In this TED video, sleep expert Matthew Walker carefully breaks down the sleep stages along with a description of why each is important. He finishes the discussion by examining the consequences of altered or decreased sleep, and why seemingly small alterations in our sleep patterns can have outsized effects.

What happens when we sleep

Sleep is a highly specialized and complex process that begins via signals from a region of the brain called the hypothalamus. As explained in this overview video from The Economist, the hypothalamus maintains our circadian rhythm by using light cues from our environment to regulate sleep via a compound known as melatonin. Once asleep, the brain begins the "sleep cycle" and progresses through the four stages of sleep over and over again each night.

What sleep is for and why you can’t live without it

Sleep is one of the most important needs that humans have. The body uses sleep as a time of restoration and rejuvenation, as body tissues repair themselves, growth hormones are released, and the process continues. Brain plasticity theorists believe that sleep is also used for the processing and consolidating of new memories.

Researchers believe the brain consolidates memories, processes emotions, and plans for the future during dream states

Your brain appears to age in five distinct stages

Analysis of brain scans from about 4,000 people has helped scientists identify five major stages of our brain's maturation from birth to death. The pattern of connections inside our brains seem to shift, on average, at ages 9, 32, 66 and 83. (Some readers may experience a paywall.)

Similarities between human and animal sleep

Have you ever noticed the wide-ranging differences in sleep between humans and animals? Sleep as a necessity is present amongst all animal species, but the specific patterns of sleep vary widely. Just think of the differences between how an owl, a whale, and a horse might sleep. This helpful resource from the Sleep Foundation explores the relations between human and animal sleep, complete with some fascinating statistics about sleep patterns throughout the animal kingdom!

A quick technical overview of insomnia

Insomnia is one of the world's most common sleep disorders. Characterized by difficulties falling and staying asleep, long-term struggles with insomnia can prelude or contribute to health difficulties. Treatments range from sleep hygiene management and relaxation therapy, and medication, including antidepressants and melatonin.

How dreams affect your memory

In 1999, scientists conducted a study in which participants were asked to recall images flashed before them for milliseconds. They found that participants who slept before recalling the information performed better than those who had been asked to recall the same information that same day. This was some of the earliest convincing evidence of how crucial sleep is for learning and memory, findings that current research continues to strengthen.

Explore a series of bedtime exercises to improve sleep

Low-impact, mindful movements can potentially help the body and mind relax before sleeping. Such exercises could be a helpful complement to regular exercise during the day.

What are the phases of migraine?

Migraine attacks don't happen all at once. This interactive walks users through the phases of migraine. Scroll through this visual guide to migraine phases to learn more about migraine, related symptoms, and brain activity.

Studies suggest when you sleep is as important as how much you get, and syncing with your circadian rhythms may lead to less fatigue and improved long-term health outcomes

A beginner’s guide to the brain

Small but powerful, the brain constitutes only about 2 percent of the human body. However, it runs jus about everything, day and night, all year round. Learn about the different parts of the human brain, as well as its unique defenses, like the blood brain barrier in this four-minute video.

Emulating Earth’s light-dark cycle is important for astronaut health and safety

Astronauts aboard the International Space Station experience 16 daily sunrises, but scientists have learned to try to promote circadian rhythms by phasing through several light settings aboard the ISS to improve astronauts’ sleep and productivity.

Understanding the distinctions between coffee types

If you’ve ever felt overwhelmed looking at a coffee shop menu, you're not alone. Here's a breakdown between common coffee styles. Click through the link to see similar guides to espresso and cold drinks.

The science behind why some noises have color names

Different noise colors (white, brown, pink, blue) have been proven to affect mood and focus. An audiologist explains that these sounds are named after specific light wave frequencies. While individual preferences vary, certain noises consistently impact sleep, stress reduction, cognitive performance, and problem-solving. The article highlights how these sounds can enhance productivity, relaxation, and even gaming experiences.

For centuries, it was common to sleep in two shifts: a few hours at the beginning of the night, and a longer period beginning around midnight

Take a quiz to discover your brain care score

Each year, nearly 800,000 Americans have a stroke. With such a high occurrence rate, you may be asking yourself what you could do now to prevent a future stroke. Researchers at Harvard collaborated to answer this question by coming up with a "Brain Care" scoring system. Take the quiz to learn the quality of your brain health today and pick up helpful insights to lower your risk of stroke and dementia well into the future.

How the brain processes a calendar year

When most of us picture a calendar year, we have a foggy image in our minds of the months, in rough, calendar-like grids. But for some folks, that picture is a whole lot more clear. Around 1 percent of the population has a strange ability known as "calendar synaesthesia," which means they're able to visualize in crisp detail an elaborate calendar of the months of the year. Learn how it works here.

Visualizing how we dream via Google search trends

When dreams perplex us, we often want to understand them—and in the age of Google, millions go to its search engine to find answers. Now, researchers have compiled a decade's worth of dream-related queries to glean dream trends across seven languages. See what dream was most commonly searched in Arabic in 2015, or what fears and hopes are specific to one culture and time alone with this unique visual essay.

The benefits of lucid dreaming

Lucid dreams happen when the dreamer knows they've stepped out of the bounds of waking life. Studies show it can help dreamers cultivate creativity, process grief, and work through trauma. A 2021 study found that 85% of participants with PTSD no longer qualified for the diagnosis after a week of trauma-informed lucid dreaming in which they intentionally witnessed (and therefore integrated) recurring nightmares or changed the outcome completely.

A map of the Milky Way

Curious about the layout of the cosmos? This resource presents a detailed map of our galaxy, the Milky Way. Learn the basic structure and identify prominent global clusters, nebulae, main arms, spurs, and constellations. With numerous different maps and mediums, get oriented with the universe’s configuration and where exactly we fit into it.

Learn about 12 basic yoga postures

A typical yoga class runs students through a sequence of basic postures, also known as asanas. This illustrated guide outlines 12 poses—including the “plough,” “fish,” and “crow”—and breaks down the specific benefits.

How stress affects every organ in the body

If you are a visual learner, this resource is for you. Not only does this article from the World Economic Forum outline the causes of modern stress along with helpful strategies, but they have created an approachable infographic to show exactly how stress manifests throughout our different bodily systems. Pair this visual guide with our other resources to gain a deep knowledge of stress and the human body.

When to see a doctor over memory lapses

Memory includes various, distinct functions, like working memory (storing information temporarily) and procedural memory (your body's ability to perform a task unconsciously). Forgetting a word or losing your keys can feel like red flag memory lapses, but they are, in fact, language or attention problems, not memory ones. However, a lapse on top of stress, lack of sleep, chronic dysfunction, or an injury may be a red flag to see your doctor.

Learn how stablecoins function in just 4 minutes

This video explains the basics of stablecoins in a beginner-friendly manner. It also dives a bit deeper into the larger stablecoin landscape, detailing, for instance, the many stablecoins backed by fiat currency other than the US dollar, like the euro, the Turkish lira, and the Singapore dollar.

13 unanswered questions about black holes

Here's a quick rundown on black hole basics, the cosmic enigmas digesting massive swaths of the universe and destabilizing our fundamental ideas of space, time, and matter. Learn how they got their name, what happens in the unfortunate instance you fall into one, and more with this list of 13 questions about black holes.

The science behind ghosts, explored

Every culture has them—restless spirits, haunted houses, things that go bump in the night. But why do we believe in ghosts? Psychologist and skeptic Dr. Chris French joins host Sony Kassam to explore the science behind the supernatural, from sleep paralysis and hallucinations to the brain’s pattern-making instincts.

Learn how your body is, scientifically, like a firework with its own slow, controlled burn.

Learn how to read a prospectus, the juicy document that any company must file with the SEC before going public.

Alzheimer's can lead to brain shrinkage, with an average of around 2% of volume reduction per year

In recent years a child anxiety expert has created and tested a novel phobia and anxiety treatment approach for children, focused on changing how parents respond to the fears.

Visualize the path of every solar eclipse from 1900 to 2099 and see what each looks like when observed from different locations on Earth.

This poison ivy knowledge quiz—accompanied by photos of the plant's varied forms—may help you identify this common rash-inducing growth.

According to the physics of black holes, our 4D reality may be a hologram—a projection of information coded on a 2D surface on the edge of the universe.

The first steps to rebuilding your credit score include getting to know exactly what's on your credit report and figuring out how far you are from the '700 club,' or 'good score' range.

See how each of the more than two million known species relates to each other—and to common ancestors—in this zoomable tree of life.

Netflix profits when you're not watching, and its movies are designed that way—read a detail-rich critical essay exposing lesser-known Netflix takes

The Dracula character, now seen as the vampire archetype, was inspired by a seafood-induced nightmare its creator experienced.

When you complete a CAPTCHA on a website to prove you are human, you may be unknowingly training algorithms for self-driving cars, whose systems require training data to help identify crosswalks, bicycles, and other outdoor objects.

The syncytiotrophoblast is the outer layer of the placenta and the largest human cell, spanning an area about twice that of a king-sized bedsheet.

The hormonal disorder PCOS was renamed PMOS in 2026, a move designed to improve care and research by shifting the focus to the hormonal causes of this condition that affects 1 in 8 women.

Before humans, the Soviet Union and the United States sent animals—including apes, dogs, and cats—to space during the Space Race.

Apeirophobia is an overwhelming fear of living forever, perhaps stemming from the brain's inability to conceptualize an infinite life.

Take a 3D tour of the Hajj, Islam's annual pilgrimage to Mecca, undertaken by over 1.5 million Muslims.

The US Constitution is widely regarded as the longest-standing written national constitution still in force—see how it has influenced rights worldwide.

Hear 50 years of iconic hip-hop samples, the genre's foundational looped tracks

A 2019 Facebook event called on attendees to "Storm Area 51, They Can't Stop All of Us," resulting in countless memes, the creation of a music festival, and eventually the arrests of those who did try to approach the area.

Explore a list of the 100 best novels of all time, compiled by some of the world's best living writers, including Salman Rushdie, Stephen King, and Jennifer Egan.

Budweiser stores yeast derived from the original 1800s strain in a secret bunker, which only the Head of Yeast Management can access—not even the CEO