The Pentagon has developed a shape-shifting wheel to make life easier for troops travelling over difficult terrain.
A military truck in which the driver can switch the wheels to a more triangular shape and back again has been demonstrated by the defense advanced research projects agency.
The shape-shifting rear wheels give the vehicle track-like grip on soft or slippery terrain, but can be converted back to a more traditional round shape in two seconds for harder surfaces.
The idea is part of a program called ground x-vehicle technologies that aims to replace the aging Humvee with a lighter, faster vehicle that can adapt to 95% of terrains.
As well as changing shape, researchers have also designed a small engine that can fit inside the wheels to boost acceleration and manoeuvrability.