 The Rock-a-Stack is designed to teach young children about colors and to help them develop their hand-eye coordination and shape perception.Since the introduction of Rock-A-Stacks in 1960, over 40 million have been sold.While Ernest Thornell was the Fisher-Price designer of this toy (from a phone conversation on 8-31-16 between Ernest Thornell and Eric Smith), the Rock-a-Stack is stylistically similar to the earlier Rocky Color Cone wooden stacking toy designed in 1938 by Jarvis Rockwell (brother of Norman Rockwell) for Holgate Toys.