Try this experiment from The EVERYTHING KIDS’ SCIENCE EXPERIMENT BOOK, and prepare to be amazed!

When a banana decomposes, bacteria flock to it. Bacteria are so small you can’t see them eating the banana. But they give off a gas which inflates the balloon.

This experiment can be performed using things around the house – a balloon, a banana, a bottle, a bowl, and a potato masher. Sit back, and watch it grow!