Maslow's Hierarchy of Needs
Maslow's hierarchy of needs is a theory in psychology proposing that human motivations are arranged in levels, with basic needs that must be largely…
Capsules
Trending now
Most recent activity
Settled science
Verified facts and proven results
Open questions
Hypotheses under investigation and ideas still debated
Debunked
Claims the evidence overturned
Theories explained
Well-substantiated explanations of how things work
Browse all
Every capsule
The Human Heart
The human heart is a muscular pump, roughly the size of a clenched fist, that drives blood through the body every moment of life. Beating around…
Nature versus Nurture
The nature versus nurture debate asks how much of who we are, our intelligence, personality, talents, and behavior, comes from our genes, and how…
Black Hole
A black hole is a region of space where gravity is so intense that nothing, not even light, can escape once it passes a certain boundary. They are…
Dolphin
Dolphins are highly intelligent marine mammals, members of the same group as whales, found in oceans and some rivers around the world. Playful,…
Elephant
Elephants are the largest living land animals, instantly recognisable by their long trunks, fan-like ears, and curving tusks. Three species survive…
The Printing Press
The printing press is a machine for transferring ink onto paper to reproduce text and images quickly and in large numbers. Its development in Europe…
DNA (Deoxyribonucleic Acid)
Deoxyribonucleic acid (DNA) is the molecule that carries the genetic instructions used in the growth, development, functioning, and reproduction of…
The Dyson Sphere
A Dyson sphere is a hypothetical megastructure that an extremely advanced civilization might build around a star to capture a large share of its…
French Revolution
The French Revolution (1789–1799) was a period of radical political and social upheaval in France that ended the Bourbon monarchy, abolished feudal…
Vaccines
A vaccine is a preparation that trains the immune system to recognize and fight a specific disease before the body is ever exposed to the real…
Tiger
The tiger is the largest of all the cats and one of the most powerful and recognisable animals on Earth. With its burning orange coat marked by bold…
The Eiffel Tower
The Eiffel Tower is a wrought iron lattice tower in Paris, France, and one of the most recognized structures in the world. Standing about 330 metres…
Pasteurization
Pasteurization is the process of heating a food or drink to a specific temperature for a set length of time in order to kill harmful microorganisms…
Grand Canyon
The Grand Canyon is one of the most spectacular landscapes on Earth: an immense gorge carved by the Colorado River through the high plateau of…
Giant Panda
The giant panda is a bear native to the mountain forests of central China, beloved worldwide for its distinctive black-and-white coat and gentle,…
Nelson Mandela
Nelson Mandela was a South African anti-apartheid revolutionary and statesman who served as the country's first democratically elected president.…
The Four Color Theorem
The four color theorem states that any map drawn on a flat surface can be colored using only four colors in such a way that no two regions sharing a…
Spontaneous Generation
Spontaneous generation was the long held belief that living organisms could arise directly from non living matter. People thought maggots formed from…
Domestic Cat (Felis catus)
The domestic cat (Felis catus) is a small carnivorous mammal of the family Felidae, descended from the African wildcat and domesticated approximately…
Nile Crocodile
The Nile crocodile is a large reptile found across much of Africa and the continent's largest freshwater predator. An ambush hunter that has changed…