Forty to 110 minutes of deep sleep is recommended per night

The REM cycle happens around four to six times per night

Sleep is a natural process that is critical to maintaining life—a process conserved throughout evolution across just about any animal with a brain. Generally speaking, the first three stages involve increasingly deep phases of non-REM sleep, followed by a roughly 90-minute period of REM sleep that repeats throughout the night.

We dream for around two hours each night, on average

Every night we lie down to rest, we spend about two hours traveling through seemingly real experiences as dreams bubble up from our subconscious during various phases of sleep. Despite the ubiquity of the experience, where dreams come from—and what their purpose is—remains largely unanswered.

How much sleep do you need?

When it comes to how much sleep you need, age matters—and, for your health, it's important to be well rested. Young children between the ages of one and three need the most sleep: It’s recommended that toddlers get between 11 and 14 hours of...

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

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

Sleep is often viewed individually, when its impact and meaning may be more communal

At any given point, roughly 2 billion people may be asleep on Earth. The typical scientific description of sleep focuses on its individual impact, but the phenomenon shapes whole cultures and eons. This essay prompts a fresh rethinking of the importance of sleep for humanity.

The lost medieval habit of 'two sleeps'

While most people accept a single seven-to-nine-hour nightly slumber is ideal, the approach is a relatively modern idea. For centuries, interrupted sleep was the norm, with historians uncovering descriptions of two periods of sleep during the normal 24-hour cycle.

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

Some animals seem to live well on little sleep

African bush elephants typically sleep for about 2 hours per 24-hour day, coming in well under a human's recommended seven-hour minimum. Other animals also appear to skimp on sleep, by human standards, without the consequences humans associate with being sleep deprived. This academic article details the sleeping habits of animals that appear to thrive on fewer than 40 winks and explores whether their sleep processes are just built different.

High-quality sleep is effectively a superpower

Sleep is critical to maintaining healthy biological functions. From restoring energy to consolidating memories, aiding immune system functions and balancing hormone production, optimizing sleep habits are one of the most important ingredients to healthy living.

External factors, not aging itself, lead to sleep loss in older adults

Though it is often believed that people need less sleep as they age, the recommended sleep guidelines for all adult age groups are almost identical. However, factors such as medication use, lack of physical activity, and loneliness can lead to sleep problems, and thereby lead older people to believe that they actually need less sleep than they do.

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.

The brain will attempt to rest itself in periods of chronic sleep deprivation

Skimping on sleep lengthens reaction times and blunts decision-making skills. At a certain point, the brain will try to sneak sleep where it can, shifting sections offline even as you remain awake. Going without sleep raises blood pressure, undermines the immune system, and increases one's risk of dementia.

About 10%-15% of people experience chronic insomnia

How often would you say you struggle to stay or fall asleep? If it's more than three times per week (and has been going on for at least one month), then you might have one of the most common sleep disorders: insomnia.

A third of US couples have opted for a 'sleep divorce'

A 2023 survey of roughly 2,000 US adults showed roughly a third of the participants opted to stay in a different room from their partner at night. Reasons for the so-called "sleep divorce" varied, from snoring issues to offset schedules. The survey, run by the American Academy for Sleep Medicine, also revealed the most sleep divorces within millennials. See the study for more on this change in sleep habits.

The human brain only uses 5% more energy during active tasks versus resting

Despite only being 2% of the weight of a human body, the average adult brain consumes 20% of its energy, with the majority of it spent on maintaining homeostasis—the stable equilibrium conditions of temperature, acidity, blood sugar, and other properties in the body. For infants, the consumption is closer to 50%.

How to end bedtime procrastination

Finally done with external obligations, you might plop onto the sofa and dive into a hobby or bit of media, pushing past sleepiness to have some time to yourself and enjoy doing what you want. This is known as "revenge bedtime procrastination," a behavior that feels relaxing but impairs sleep hygiene.

The evidence for the best sleep positions

For a behavior so crucial to human health, sleep positions are reportedly understudied by researchers. This article summarizes some of the more recent studies, taking into account the various forms of problems encountered during sleep: neck and back pain, snoring, acid reflux, and facial skin damage. Most studies point to side-sleeping as the most optimal, with sleeping on one's front as the least helpful. Read the piece to see which position is best for you.

Artificial lighting and modern practices like working late are linked with sleep shifts

An analysis of five adults participating in a German reality program that tasked them with living in a Stone-Age-like settlement for 2.5 months, provided some insights into how modern conditions may have shifted our circadian rhythms. The participants slept about 90 minutes more under these conditions, and went to bed earlier and rose earlier, raising questions about how circadian rhythms, sleep, and sleep quality are affected by modern lifestyles.

Obsessing over sleep metrics leads to worse sleep quality

Over one-third of Americans have used wearable technology to track their sleep, and the anxiety over having perfect sleep data, or orthosomnia, has made getting a good night's sleep more difficult. Experts agree that most devices cannot correctly assess sleep details, making the data unreliable.

Sleep paralysis occurs when the body fails to 'unfreeze' in sync with waking

When the body falls into a deep enough phase of sleep, it paralyzes certain parts of itself so the brain can't force it to physically act out dreams. This well-known but little-understood phenomenon happens when the brain awakens early and typically results in haunting hallucinations and reports of supernatural terrors.

Hotels around the world now offer packages focused especially on sleep

A Belmond Hotel in London, for example, has partnered with a meditation and holistic coach to create a service called the Sleep Concierge, which includes meditation recordings, a pillow menu, and the option of a weighted blanket, among other customized options. Medical experts believe that hotel experiences such as this one can be beneficial to those lacking sleep, provided certain provisions (such as an on-call medical professional) are also provided.

Adults need two days of muscle strengthening activity weekly—yet most of us aren't doing that

That recommendation—muscle-strengthening activities on two or more days a week working all major muscle groups—is in addition to 150 minutes weekly of moderate-intensity physical activity. Those resistance and aerobic training numbers from the US government are echoed by other medical groups. But nearly 80% of adults aren't checking the box on those goals. This failure is linked to about $117B in annual health costs and some 10% of premature mortality.

What is the 70-20-10 budget?

The 70-20-10 budget rule dictates that people should spend 70% of their income on needs, 20% on savings, and 10% on wants. It's a new take on the 50-30-20 budget, which claims people should aim to spend 50% of their income on needs, 30% on wants, and 20% on savings. Learn more about this budgeting strategy by reading this article.

See who Americans spend time with over their lives

Time with friends peaks in the teens and falls sharply by the 30s, while time with coworkers dominates middle age. After retirement, both nearly vanish, and time spent alone climbs steadily to nearly 8 hours a day by age 80.

How specialized oxygen mixtures like heliox enable deep diving without feeling drunk

Beyond a depth of about 30 meters (98 feet), if divers are breathing surface air, which is about 78% nitrogen, underwater pressure forces more nitrogen into the bloodstream and induces nitrogen narcosis, whose symptoms resemble alcohol intoxication. Through saturation diving, where nitrogen is replaced with helium—an inert gas—deep divers can maintain cognitive function while working for extended periods.

Antiperspirants work better if they are applied at night

Dermatologists recommend applying antiperspirant at night for the best results. When applied to clean, dry skin at night, the active ingredient in most antiperspirants (aluminum salt), combined with the skin's natural moisture, forms plugs that block sweat glands, limiting sweat and related odors.

The average TikTok user spends 95 minutes on the app per day

According to HubSpot, the average TikTok user spends 95 minutes per day using the app, and an estimated 90% of users access TikTok daily. TikTok also has the highest average session length among social media platforms: Its users spend almost 11 minutes per session.

About 12.5% of US adults experience a phobia in their lifetime, a diagnosis that hinges on the intense fear interfering with daily life and persisting for at least six months.

Use this calculator to find the dollar value of your mental load, from meal planning to coordinating after-school care for your children.

Bone marrow (soft tissue found inside certain bones) generates roughly 500 billion new blood cells each day

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

To reduce wrinkles in clothing, research recommends gentle wash cycles with more water and tumble drying with smaller loads and longer times.

44% of Americans say they pray at least once a day—discover how your state's religiosity stacks up against the rest of the country.

US housing costs have risen by roughly 175% between 1991 and 2026—but a growing number of Gen Zers are becoming homeowners anyway. In 2025, 4% of homebuyers were Gen Z, up from 3% the year before.

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.

11 people died from firework injuries in the US in 2024.

Waves off the coast of Nazaré, Portugal, can reach over 100 feet and are caused by the area's deep underwater canyon geography

Read a deep dive on the 'all-purpose healing' peptide BPC-157.

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.

Electrical grids worldwide must double their power delivery capacity by 2050 to meet surging demand from AI and electric vehicles.

In 2026, Finland was named the world's happiest country for the ninth consecutive year based on its wealth, social safety network, and high life expectancy, among other factors.

In 1963, a basement renovation in Turkey revealed a passageway to a hidden, multilevel underground city that once housed as many as 20,000 people

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.

Track the location of the Voyager probes, currently between 13 and 15 billion miles away from Earth.

Domino's Pizza's 30-minute delivery guarantee was responsible for the chain's 1980s surge, but it was discontinued after the company was found liable for delivery driver accidents.

A small portion of The Winstons' 'Amen, Brother,' an obscure '60s gospel record, is the basis for thousands of hip-hop tracks, making it one of the most sampled records ever that's informally known as 'the Amen break.'

Objects can be 3D printed with light by projecting 2D computerized tomography (CT) scans onto rotating cylinders of resin, which solidify upon exposure.

Dirty lightning is a thunderstorm created from friction between rising and falling flows of ash and smoke during volcanic eruptions.

The US dollar is the most widely circulated currency in the world, and is involved in nearly 90% of global transactions