Nitinol, also known as Ni-Ti is one of several shape memory alloys available. The shape memory effect comes from the mixture of nickel and titanium transferring between the martensite and austenite phases of crystal structure. Basically, what this looks like is you have a wire that you can straighten, bend into any shape, mash, etc. and then place it in hot water to watch it come back to its original shape. The uses for this are endless. Uses include robotics, heat engines, science projects, practical jokes, artery stents for a bypass surgery, the only limitation is your creativity.