A wavy hairdo is a popular hairstyle that can be achieved in a variety of ways. A perm is a chemical treatment that permanently changes the structure of the hair, resulting in waves or curls. The Marcel wave is a type of permanent wave that was popularized in the 1920s by French hairdresser Marcel Grateau. It is created by wrapping the hair around heated curling tongs and is still used today to create wavy hairdos.