Marbles are fun for people of all ages but a lot of folks don’t know how they are made.

Thanks to the people at How It’s Made, now you can learn all about the process.

Small balls resembling marbles have been played with by people since ancient Egyptian and Roman times. The difference today is that marbles are made out of glass because it is durable and inexpensive. Also, present-day marbles are used not only for fun but in industry.

To make marbles, glass is heated in a kiln for 16 hours with previously made marbles that were rejected because they weren’t the correct size. Segments are then cut to form slugs and they are turned into marbles of various sizes. Color and polishing are added later after marbles pass inspection.

Watch the whole video above to see how the entire process works in detail.