The chain-melted state is a state of matter in which a substance, typically a metal, notably potassium, behaves both in the liquid and solid state at the same time. This is done by applying extreme pressure and temperature, causing the metal to become solid and molten simultaneously. It was confirmed to be a state of matter in 2019 by a group of researchers at the University of Edinburgh using artificial intelligence to analyse the results of subjecting potassium to high temperatures and pressure, when the potassium began exhibiting properties where it was apparently both solid and liquid. The phenomenon was observed by a group of other researchers in 2014; however, it was only thought to be a transitioning state. The chain-melted state has also been observed in other elements, such as sodium and rubidium. Some other elements, like bismuth, are also capable of being in the chain-melted state.