Begin with a large, clear plastic or glass jar. Then toss in a few different food items, such as bread, fruit, cheese, lunch meat, cookies, chocolates, etc. Whatever you want to toss in is fine. Then spread a couple of teaspoons of water in the jar for added moisture. Seal the jar with a lid and you've started a fungus garden. Ours is shown in the picture below.
Each day over the next two weeks we'll closely examine the contents of the jar to determine which have mold growing first and how quickly. Honestly, I don't know what to expect, so I'm just as interested as my girls are. We should have result pictures to post in a week or two.