Abstract: The present invention generally relates to a mechanical structure having electronic circuits that easily and quickly connect together. The mechanical structures may be building blocks which are stackable and reusable. The building blocks may be removably held together by, for example, gravity and/or friction. The building blocks have electronic circuits which may have numerous uses, including, but not limited to educational, industrial and entertainment uses. More specifically, a building block of the present invention may be insert on, and secured to, a second building block. The building blocks may be identical or may have different features which accomplish varying desired functions. For example, a building block of the present invention may have a light and/or sound feature. In addition, the circuitry of the building blocks of the present invention has unique electronic paths which prevent electronic shorts across a power source.