Moranis plays "nutty" inventor Wayne Szalinski who perfects a machine capable of shrinking objects down to a hundredth of their size. When his two older children and the neighbors' two sons enter the room in which the shrinking machine is located in order to retrieve a lost baseball, they find it has been triggered by the ball and take the full brunt of the shrinking ray. They spend the rest of the movie trying to get back to the house after accidentally being taken out with the trash. Since they are so tiny, the trip is an epic adventure filled with a number of obstacles including "giant" insects and a runaway remote-controlled lawn mower. Towards the end of the movie, the children return to the house, where the younger son of the Szalinskis, Nick, falls into Wayne's cereal and is nearly eaten by his father.

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