What is the beginning of west side story?

West Side Story begins with a prologue that introduces the two rival gangs in the story, the Jets and the Sharks. The Jets are a white gang, while the Sharks are a Puerto Rican gang. The prologue shows the two gangs fighting, and it establishes the tension between them. The story then moves to the following day, when Tony, a former member of the Jets, meets Maria, the sister of Bernardo, the leader of the Sharks. Tony and Maria fall in love, but their relationship is forbidden because of the hatred between their two gangs.