Mass–energy equivalence

Have you ever heard of Albert Einstein? He was a very smart man who figured out something very important for science called the mass-energy equivalence.

You know how there are different things in the world like toys, food, and even you? Well, everything has something called mass, which basically means how heavy something is. For example, you are heavier than a toy and a toy is heavier than a piece of cotton candy.

Now, energy is something different. It's like when you run and play and get really tired, your body is using up energy. Or when you turn on a lamp or watch TV, there's an electricity that powers them and that is energy too.

What Einstein figured out was that Mass and energy are kind of like two sides of a coin. They can change back and forth from one to the other. So, if you take something really heavy like a brick and break it into smaller pieces, it creates energy. On the other hand, if you take energy and do something with it, like putting it into something really tiny called an atom, the atom will become heavier.

This is a really important idea that helps scientists understand how the world works. And that's what makes Einstein one of the most famous and smartest scientists in the world.