Another old movie I've seen lately was The Incredible Shrinking Man (1957). Coincidentally, it and another old film I've recently watched, The Last Man on Earth, were both based on novels by Richard Matheson.
In The Incredible Shrinking Man, Grant Williams stars as Scott Carey, a man who is exposed to a combination of radiation and insecticide which causes him to shrink day by day. As the effects progress, Carey is bitter and tormented and struggles to accept his fate.
I was quite amazed at the special effects in this 1957 film. At one stage, when Carey is about 6 inches tall he is attacked by the family cat. He barely escapes to the basement where he is trapped for some time. He continues to shrink and when he is about an inch tall he has a run-in with a tarantula spider. All the effects were quite realistic. Although Carey's life is thrown into disarray, the film does end on a positive note.
I quite enjoyed this film and it reminded me of a TV series I used to love watching when I was a kid - The Land of The Giants.