# The Atom

You probably already know that everything is made up of little tiny things called atoms. You might even know that each atom is made up of even smaller particles called protons, neutrons and electrons. And you've probably heard that atoms are small. But I bet you haven't ever thought about how small atoms really are. Well, the answer is that they are really, really, really small.

## Just how small are atoms?

To understand this, let's ask this question: How many atoms are in a grapefruit? Well, to help you visualize this, let's blow up each of the atoms to the size of a blueberry. And then how big would the grapefruit have to be? It would have to be the same size of the Earth. So how big is the atom? It's really, really, really, really small.

## What are atoms made of?

Let's now look inside of each atom. In the center of the atom is something called the nucleus, which contains protons and neutrons, and on the outside you'd see electrons.

## How big is the Nucleus?

So how big is the nucleus? So if you popped open the blueberry and were searching for the nucleus, it would be invisible. It's too small to see. So to actually see the nucleus, we need to blow up the blueberry, up to the size of a football stadium.

## The Density of the Nucleus

Make a box that is one foot by one foot by one foot and put cars into it. Now, cars on average weigh two tons. How many cars would you have to put into the box to have your box have the same density of the nucleus? The answer is 6.2 billion. That is almost equal to the number of people in the Earth.
Have you ever seen an atom?