A pioneer in educational toys, the A.C. Gilbert Co. released its chemistry set in 1923. Marketed solely to boys, the kit was designed to teach basic chemistry skills, but by today's standards, it was nothing short of a homeland-security breach. (Experiment No. 1: Explosives.) Still, it received the highly regarded Good Housekeeping seal of approval, and Gilbert went on to sell millions of sets over the next 30 years. Eventually, even girls were acknowledged by the manufacturers — but only as aspiring assistants. Gilbert's Lab Technician Set for Girls was released in the 1950s, cloaked in reassuring pink hues. It would be another 10 years until the gender barrier in kiddie chemistry was brought down and boys and girls were finally allowed to play scientist together.