In the 20th century we added an unprecedented number of years to our lifespans, but is the quality of life as good? Surprisingly, yes! Psychologist Laura Carstensen shows research that demonstrates that as people get older they become happier, more content, and have a more positive outlook on the world.

One bag of apples, one apple, one slice of apple -- which of these is one unit? Explore the basic unit of math (explained by a trip to the grocery store!) and discover the many meanings of one.

TED Studies, created in collaboration with Wiley, are curated video collections — supplemented by rich educational materials — for students, educators and self-guided learners. The Edge of Knowledge explores the fascinating implications of some of science's most perplexing theories: quantum mechanics, general relativity and attempts to unify them. Learn how scientists combine sophisticated mathematics and ambitious experimentation like CERN’s Large Hadron Collider to advance our understanding of the universe.

Long, fancy words designed to show off your intelligence and vocabulary are all very well, but they aren't always the best words. In this short playful video Terin Izil explains why simple, punchy language is often the clearest way to convey a message. A quiz, thought provoking question, and links for further study are provided to create a lesson around the 2-minute video. Educators may use the platform to easily "Flip" or create their own lesson for use with their students of any age or level.

TED Studies, created in collaboration with Wiley, are curated video collections — supplemented by rich educational materials — for students, educators and self-guided learners. In Understanding Happiness, expert explorers of the mind chart our understanding of how happiness is created and cultivated. Their insights challenge our most basic cultural, political and economic assumptions and are transforming the field of psychology.

Edgar Allan Poe, an American icon, is celebrated for his life and work. This lesson will delve deeper into his early life, his macabre short stories, his poem "The Raven," and his mysterious death in Baltimore in 1849.

Cambridge researcher Aubrey de Grey argues that aging is merely a disease — and a curable one at that. Humans age in seven basic ways, he says, all of which can be averted.

Salman Khan talks about how and why he created the remarkable Khan Academy, a carefully structured series of educational videos offering complete curricula in math and, now, other subjects. He shows the power of interactive exercises, and calls for teachers to consider flipping the traditional classroom script -- give students video lectures to watch at home, and do "homework" in the classroom with the teacher available to help.

From something as small and complex as a chromosome to something as seemingly simple as the weather, sex determination systems vary significantly across the animal kingdom. Biologist and teacher Aaron Reedy shows us the amazing differences between species when it comes to determination of gender.

TED Video: Leaps and bounds separate that which is ironic and that which many people simply say is ironic. Christopher Warner wants to set the record straight: Something is ironic if and only if it is the exact opposite of what you would expect.

TED Studies, created in collaboration with Wiley, are curated video collections — supplemented by rich educational materials — for students, educators and self-guided learners. In Visualizing Data, TED speakers shake up statistics with elegant, dynamic representations that make mountains of data comprehensible — and even exciting. Learn how to visualize data and present complicated statistics in elegant and captivating ways. Relevant areas of interest, study and coursework include: information design, demography, statistical literacy, economics, sociology, media studies, linguistics, meteorology and computer science.

TED Studies, created in collaboration with Wiley, are curated video collections — supplemented by rich educational materials — for students, educators and self-guided learners. In Reworking the Western Diet, speakers examine how that diet — processed, high in refined sugars, and heavy in corn, soy, meat and dairy — is making us and the environment sick. These TED Talks blaze the trail to sustainable farming and a more sensible diet. 

Author Isabel Allende's new TED talk is about living passionately at any age.

Ayako Suwa is intent on spreading a new concept of food that evades labels such as gourmet and nutritional. She believes that to eat is to live, but we must taste to truly evolve, and those tastes include happiness, regret, anger and more.

In the face of artificial intelligence and machine learning, we need a new radical humanism, says Tim Leberecht. For the self-described "business romantic," this means designing organizations and workplaces that celebrate authenticity instead of efficiency and questions instead of answers. Leberecht proposes four (admittedly subjective) principles for building beautiful organizations.

High school science teacher Tyler DeWitt was ecstatic about a lesson plan on bacteria (how cool!) -- and devastated when his students hated it. The problem was the textbook: it was impossible to understand. He delivers a rousing call for science teachers to ditch the jargon and extreme precision, and instead make science sing through stories and demonstrations. (Filmed at TEDxBeaconStreet.)

TED Studies, created in collaboration with Wiley, are curated video collections — supplemented by rich educational materials — for students, educators and self-guided learners. In Ecofying Cities, speakers reveal ideas about sustainable development (and redevelopment) that aren't all about setting limits, going without or preparing for the worst. Rather, they find solutions in resourceful, hopeful, beautiful communities.

At face value, the lines between verbal irony, sarcasm, and compliments can be blurry. After all, the phrase 'That looks nice' could be all three depending on the circumstances. In the final of a three part series on irony, Christopher Warner gets into the irony you may use most often and most casually: verbal irony.

Scientific discovery isn't as simple as one good experiment. The weird and wonderful history of cell theory illuminates the twists and turns that came together to build the foundations of biology.