Soma Cubes are a set of seven irregular polyhedral pieces that can be assembled into a 3×3×3 cube as well as hundreds of other three-dimensional configurations, making them a rich material for spatial reasoning and geometric problem-solving in the upper elementary years. They bridge the gap between concrete manipulation and abstract visualization, supporting children's developing capacity to mentally rotate and compose three-dimensional forms. Teachers find them particularly effective as an extension activity for children who have moved through the geometric cabinet and solid geometry materials and are ready for open-ended spatial challenges.