This TED Talk features marine microbiologist Karen Lloyd, recorded live at TED 2019.

It may seem like we're all standing on solid Earth right now, but we're not.

The rocks and the dirt underneath us are crisscrossed by tiny little fractures and empty spaces.

And these empty spaces.

And these empty spaces are filled with astronomical quantities of microbes, such as these ones.

The deepest that we found microbes so far into the earth is five kilometers down.

So, like, if you pointed yourself at the ground and, like, took off running, like, into the ground,

you could run an entire 5K race, and microbes would line your whole path.

So you may not have ever thought about these microbes that are deep inside Earth's crust,

but you probably thought about the microbes living in our guts.

So if you add up the gut microbiomes of all the people and all the animals on the planet

collectively weighs about 100,000 tons.

This is a huge biome that we carry in our bellies every single day.

We should all be proud.

But it pales in comparison to the number of microbes

that are covering the entire surface of the Earth,

like in our soils, our rivers, and our oceans.

Collectively, these weigh about two billion tons.

But it turns out that the majority of microbes on Earth aren't even in oceans or our guts or sewage treatment plants.

Most of them are actually inside the Earth's crust.

So collectively, these weigh 40 billion tons.

This is one of the biggest biomes on the planet, and we didn't even know it existed until a few

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