The Incredible Shrinking Man (1957) on Netflix

Robert Scott Carey and his beloved wife Louise Carey are spending vacation on the motor boat of his brother Charlie. When Louise goes to the galley to bring a beer to Robert, he is engulfed by a weird mist. Six months later, Robert is sprayed by insecticide and when he goes to the doctor for the routine medical examination, he realizes that he had become shorter. Then he goes to a laboratory to be examined by scientists and they conclude that the combination of the mist with the insecticide has caused the effect. When Robert is only 93 cm height, the scientists find a formula and he stops shrinking and meets the midget Clarice that gives hope to him. But soon he continues to shrink and he moves to a dollhouse. One day, Louise is not in the house and their cat breaks in Robert's house. However he succeeds to escape to the basement and Louise believes that the cat has eaten him. Robert is trapped in the cellar and he has to struggle to survive against a spider and to find nourishment.