Wayne Szalinski (Rick Moranis) is an eccentric scientist who, working at home, perfects a machine that will shrink things. His daughter, Amy (Amy O’Neill), his son, Nick (Robert Oliveri), and two neighbor boys, Ron (Jared Rushton) and Russ (Thomas Wilson Brown) Thompson go into the room with the machine while chasing their errant baseball, the ball has triggered the machine, and the four children all shrink to 1/100th of their normal size. The children try to get their parents to notice them; instead they are inadvertently thrown out with the trash. Now they must travel through the back yard in order to get back to the house and get help. They find the yard they’ve played in so often can be a very treacherous place when insects are larger than they are, water from a hose causes a flood, and a robot lawnmower is running around over their heads. At long last the kids make it into the house again and are faced with the task of getting the attention of their parents. When Nick falls into his father’s cereal bowl and is almost eaten, Wayne finally notices him and is able to restore the children to their normal sizes.