 Spin crossover compounds are molecules that can switch between two different magnetic states when exposed to certain conditions. These conditions include temperature, pressure and light. When these compounds are exposed to heat, they change from one magnetic state to another. This process is called spin crossover. It has been observed in many different types of compounds, including monodash, oligodash and polynuclear iron, two complexes in cages, polymeric 1D, 2D and 3D systems, nanomaterials and polyfunctional materials. These compounds have been used in various applications, such as thermal and pressure sensors, optical devices and magnetic recording media. This article was authored by Philip Dutledge, Anabee Gaspir and Jan Garcia.