This plastic platform acts like water, rubber, sand, and more.
MIT's Materiable is a digital sandbox for the physical world.

MIT’s Materiable is a high tech, low res, shapeshifting interface.
Individual “pins” look like tall, narrow piano keys. Collectively, they look like pixelated water— or rubber, or sand. Touch them and adjoining pieces react accordingly. Flexibility, elasticity, and viscosity are all programmable. As a ‘multimaterial’ it can represent topography and water in a landscape, or function as a medical simulator. Aesthetically, Materiable is simple. With some imagination, the possibilities are elaborate—and unlimited.

MIT’s Tangible Media Group does projects (like Materiable) in pursuit of ‘Tangible User Interfaces’, “embodying digital information in physical space.”