Schrödinger's cat is a thought experiment conceived by physicist Erwin Schrödinger in 1935, designed to illustrate the concept of superposition in quantum mechanics. In the thought experiment, a cat is placed in a sealed box with a radioactive atom, a Geiger counter, and a vial of poison. If the atom decays, the Geiger counter triggers the release of the poison, resulting in the cat's death. If it does not decay, the cat remains alive.