Kids of all ages are entertained by toys that are just smaller versions of everyday items -- eg. toy cars, model trains, tiny dollhouses, etc. Most kids outgrow this fascination with small things when they get bigger, but some folks don't. Plenty of adults work on building small, intricate designs... that can be artwork or technology. Here are just a few examples of people using their imaginations to create almost incredibly tiny worlds that everyone should be able to appreciate.
If you'd like to read more awesome and interesting stuff, check out this unrelated (but not entirely random!) Techdirt post