Micron supports Engine 20 through a chain of missions; Time limited races through the Blue Course (a tutorial for how you get through can be here) . A total of 10 races are needed, each with a shorter time limit, to obtain Engine 20. Also unique "Micro" gear is available in Micron - like the "Micro Really Big Laser". Speedy Gonzales used to spawn here. Because of the fact that if Speedy was killed, all players doing the race course would get locked out of Micron, therefore having to wait 24 hours to come back in and keep going, Speedy was moved to his own little galaxy within Micron.
Micron is made up of several "solar systems" that are miniaturized. Everything from the warps to the base to all planetary bodies are much smaller than they should be.