Innerspace

Test pilot Tuck Pendleton takes part in an experimental procedure that shrinks him to a microscopic size inside a special vessel. However, due to an accident, he is injected into the body of Jack Putter, a nervous man who worries excessively about his health. Inside Jack's body, Tuck must persuade him to locate his ex-girlfriend, Lydia Maxwell, so she can assist in safely extracting Tuck and the vessel and restoring them to their normal size before Tuck's oxygen supply runs out.