From the brains behind brains on, this is the moment of um.

Answering those questions that make you go um.

Um, um, um, um, um, um, moment of um comes to you from APM Studios. I'm Anna G.

Before I joined the Brains-on team, I used to have a pretty different job. I was an archaeologist.

That's a scientist who studies how people lived in the past by finding old things ancient people left behind. I was part of teams

digging for ancient stuff in places like France and South Africa. I also taught archaeology to college

students. One of my favorite things to teach was the study of the human

skeleton. Thanks to the years I spent teaching, I know a lot about human bones. For example,

did you know that when babies are born? They don't have kneecaps. That's a bone that we grow

later when we're toddlers learning to walk. Or did you know that there are seven whole bones that form the part of the

skull where the eyeballs go? Now, I might be a bone expert, but when it comes to the other parts of the

body, like muscles and organs and, well, eyeballs, I don't know much. That's why I was so excited

to get this question from listener Gianna.

Do eyeballs grow?

Oh, yeah, eyeballs grow a lot.

They grow by about 50% from when you're born to when you're 20, 21 years old.

I'm Dr. Stacey Pinellas.

I'm a professor of ophthalmology.

Optomology is a kind of doctor that treats eye problems and kids and does eye surgeries.

When babies are born, their eyes are usually about 16 millimeters, which is like 1.6 centimeters.

So they start off around that size, and they grow a lot over the first

two or three years of life. And that's why when babies are born, their vision is not that good.

...