who has changes and why?

Gregor has changed into an insect. The first sentence of the story is intended to shock. In Kafka's view, we are all frozen inside and literature should be the axe that smashes the ice. This first sentence-one of the most famous first sentences in modern literature-certainly breaks the ice. Reading it, we know from the start that we cannot anticipate the events of this story; all our normal expectations of literature are instantly stripped away. The most natural response is to try to understand how Gregor Samsa could have been transformed into an insect overnight, but neither an answer nor any hint at one is offered.