Compressing a semiconductor to bring atoms closer together or stretching it to move them farther apart can dramatically change how electricity flows and how light is emitted. Scientists found an innovative way to compress or stretch very thin (monolayer and bilayer) films of tungsten diselenide by placing the film on different surfaces at high temperatures. The underlying surface stretched or compressed upon cooling. Why? With few exceptions, all materials expand when heated and contract when cooled. However, this change happens at different rates. Because the films respond at a different rate than the surface, the films stretch or compress upon cooling. Excitingly, the electronic properties of the stretched films were dramatically different.