Boys and girls dress in Kimono and go to their local shrine on Shichi-Go-San. They are given a special type of candy that symbolizes healthy growth and longevity — Chitose Ame ("thousand year candy").
In the past, children under 3 years old were required by custom to have shaven heads. The ceremony celebrates the child reaching the age that they can start to grow their hair and wear kimono or hakama (men's kimono).
These days, it's also common for boys to wear a suit for Shichi-Go-San.