Final answer:
The sexual revolution began in the 1920s with changes in gender relations and sexual expression.
Step-by-step explanation:
The sexual revolution began in the 1920s with changes in gender relations and sexual expression. This period saw an increasing agency expressed by women and changing social customs that grew more permissive. Young men and women engaged in sexual exploration, and new words like "petting" entered polite society. The sexual revolution continued to evolve in the following decades, with significant growth in the late 1960s.