In which John Green teaches you about the Holy Roman Empire by teaching you about Charles V. Charles Hapsburg was the holy Roman Emperor, but he was also the King of Spain. And the King of Germany. And the King of Italy and the Lord of...

In which John Green teaches you about Imperialism, but not from the perspective of the colonizers. This week John looks at some Asian perspectives on Imperialism, specifically writers from countries that were colonized by European...

In which John Green teaches you about water! So, we talk about resources a lot on Crash Course, and today is no exception. It turns out people can't live without water, which means it's absolutely necessary for civilization. Today John...

In which John Green talks about the methods of writing history by looking at some of the ways that history has been written about the rise of the West. But first he has to tell you what the West is. And then he has to explain the Rise of...

In which John Green teaches you about how Islam has interacted with politics during it's history, and how it continues to do so today. Islamist movements are in the news a lot lately, but how did that happen. John will point out that...

Walking through the hallways at the Native American Community Academy in Albuquerque, New Mexico, students see leaders and teachers like Arlyn John who share their cultural background. Joined by some of his students, he shares his Brief...

I was in Arizona recently for Phoenix Comic-Con, and had the amazing pleasure of seeing one of Earth's greatest natural wonders… the Grand Canyon. More than a mile deep, and several miles across, it just defies belief. But I couldn't...

If you tried to sum up the last 150 years or so in one image, a chart of exponential growth would be a good place to start. It shows that some things change faster over time. You could apply it to life expectancy. Or compound interest....

More people have food allergies than ever before. Peanuts, tree nuts, shellfish, eggs, and even milk… the list of possibly dangerous foods seems to get longer every day. But why do some people’s bodies have deadly reactions food? And why...

Humans have a hard time with really big numbers, especially when it comes to DEEP TIME. The history of the Earth took a lot longer than you think, trust me. But I’m here to help you put it in perspective. With some string.

How do you make a Grand Canyon?

If everyone would just put more in the recycling bin instead of the trash can, the world would be a better place. Right? Well, that’s not exactly true. For many items that end up in the recycling bin, you’ve actually created more trash...

People say insects are the food of the future. They’re more environmentally sustainable and more humane than other sources of animal protein. Can they really catch on in western diets? I’m a pretty adventurous eater, but I’ve never...

Walk into any forest, and beneath your feet is an elaborate social network that helps make life on Earth possible. It’s called the “Wood Wide Web”, a massive and intricate network of fungi that exchange water, nutrients, and chemical...

In almost every animal species on Earth, equal numbers of males and females are conceived. Why is that? Especially in populations like lions or elephant seals, where most males don’t get to mate? That’s survival of the laziest, not...

Visiting the Largest Bat Colony on Earth!

Looking up at the stars makes you wonder: what and who is out there? And why haven’t we seen any other intelligent civilizations given the vast size and age of the universe? They’re complicated questions and although we haven’t met any...

The first thing a baby giraffe experiences after being born is a 2 meter fall straight down to the ground. But within an hour, it’s standing, walking, and nursing on its own. And a blue whale calf, after nearly a year growing inside mom,...

The eyes are often the first thing we see when we look at someone. And when you look at them up close, everyone’s eye color is a kaleidoscope of shapes and hues. How does eye color work? The answer involves some very cool physics, and...

If we lived light years from Earth, how would we know there’s life here? Let’s take a look at the search for extraterrestrial life on habitable exoplanets, and discover what biosignatures would show someone else that we’re here.

It took about a century for black holes to go from impossible, to theoretical, to real. And it was just this year, in 2019, when we finally saw the first picture of a black hole! But how to you take a photo of something so massively...

Seemingly distant ecosystems, even half a world apart, are connected in surprising ways. In this special limited series, Emily Graslie and Trace Dominguez join me as we explore the universal rules of life that tie together Earth’s living...

Seemingly distant ecosystems, even half a world apart, are connected in surprising ways. In this special limited series, Emily Graslie and Trace Dominguez join me as we explore the universal rules of life that tie together Earth’s living...

I’ve explained a lot of weird bodily functions on this show but there’s one that we haven’t covered that’s always confused me: Tickling. What are you for, tickling? What’s the point of you? Why do you exist? Why do you make us laugh even...