You probably have a vague idea of what sperm does, but not all sperm are created equal, and some have even developed unique adaptations to get where they're going.

After many adventures in Wonderland, Alice has once again found herself in the court of the temperamental Queen of Hearts. She's about to pass through the garden undetected, when she overhears the king and queen arguing that 64 is the...

Scientists found a species of wheatgrass that is resistant to fungus, but how it became resistant is both surprising and unclear.

John Green teaches you about Virginia Woolf's modernist novel, To the Lighthouse. Let's face it. You're not reading To the Lighthouse for the plot. There's not a whole lot of plot, unless you count the tension about the beef stew. You're...

Jessi and Squeaks are ready to go outside, but before they do, Jessi needs to make sure to put on sunscreen so that she doesn't get a sunburn!

David Hanson's robot faces look and act like yours: They recognize and respond to emotion, and make expressions of their own. Here, an "emotional" live demo of the Einstein robot offers a peek at a future where robots truly mimic humans.

Equipped with unique adaptations that make them both good at hunting and getting their creep on, owls are totally the ninjas of the bird world.

Why do we often wait so long to recognize each other's gifts? Why are the truest compliments for the people we love often said only after they're no longer around to hear and savor them? Andrea Driessen makes the case for writing...

Paul Andersen steps you through eight types of animal behavior. He starts by defining ethology and explaining that behavior varies from innate to learned. He discusses each of the following with examples; instinct, fixed action...

Our bodies function necessarily under the presence of gravity; how blood pumps, a sense of balance and bone growth are all due to life in a world where gravity is an inescapable reality. Armed with experiments from neuroscientists David...

Mr. Andersen explains the Central Dogma of biology. He shows how DNA is transcribed to form mRNA and how mRNA is translated into a protein.

Paul Andersen gives you a brief introduction to the cell membrane. He starts by describing amphipathic nature of a phospholipid and how it assembles into a membrane. He gives an overview of the fluid mosaic model inside cells. He...

Have you ever heard of a Perpetual Motion Machine? More to the point, have you ever heard of why Perpetual Motion Machines are impossible? One of the reasons is because of the first law of thermodynamics! In this episode of Crash Course...

Paul Andersen starts by defining transpiration as evaporation off of a leaf. He then describes how a potometer can be used to measure the rate of transpiration in different environments.

We've reached the grand finale of our four part series on human reproduction: BABIES! Today Hank walks you through the stages of pregnancy, beginning with how a zygote develops into blastomeres to a morula to a blastocyst and finally to...

Before there was Google, there were encyclopedias. The very idea of these vast collections of knowledge can be credited to Pliny The Elder. So who was he, and why does he seem to pop up everywhere from Alchemy to Zoology? Hank has the...

One of the problems with the whole idea of a single Scientific Revolution is that some disciplines decided not to join any revolution. And others just took a long time to get there.

Scientists have learned more about why royal jelly makes queen bees, and we peek at the tiny and terrifying mandibles of trap-jaw ants.

Craft along with Jessi and Squeaks to make your own insect art!

We’ve covered a lot of incredible stuff, but this week we’re talking about the weirdest objects in space: BLACK HOLES. Stellar mass black holes form when a very massive star dies, and its core collapses. The core has to be more than...

Rhiannon Giddens pours the emotional weight of American history into her music. Listen as she performs traditional folk ballads -- including "Waterboy," "up Above My Head," and "Lonesome Road" by Sister Rosetta Tharp -- and one glorious...

In which John Green teaches you, at long last, about the most exceptional bunch of empire-building nomads in the history of the world, the Mongols! How did the Mongols go from being a relatively small band of herders who occasionally...

Hank introduces us to some freaky parasites that use mind control to hijack the brains of their hosts.

In this video Paul Andersen explains how heat is the movement of energy from an object with a higher temperature to an object with lower temperature. Heat transfer can occur through conduction, convection, and radiation.