When kids click together these chunky pieces and then flip the switch, they'll get an exciting result: either a spinning fan, a glowing light, or a whistling siren! All switch blocks and action tops are interchangeable for mixing, matching and experimenting with actual working circuits in a completely safe way. Young children will develop an innate understanding of circuitry and build a strong foundation for future STEM success. Requires 6 AA batteries (not included).