Big enough to do the job

Not every rocket has to be a towering giant. The kids and I have had a lot of fun with Quest MicroMaxx rockets and motors, which are 1" long and 1/4" in diameter. Our smallest rocket is about the size of a crayon with fins, although they can get even smaller. Or how about a rocket glider that weighs in around 2 grams?

Of course, not every crayon rocket has to be tiny either.

Now these guys are building tiny motors, both rotary and rocket. They talk a little bit about why to miniaturize this much (more here). Not too shabby for Berkely boys.