Indium was discovered by the German chemists Ferdinand Reich and Hieronymus Theodor Richter in 1863. Reich and Richter had been looking for traces of the element thallium in samples of zinc ores. A brilliant indigo line in the sample's spectrum revealed the existence of indium. Indium is about as abundant as silver but is much easier to recover since it typically occurs along with zinc, iron, lead and copper ores.

Indium is used to coat the bearings of high speed motors since it allows for the even distribution of lubricating oil. Indium is used to dope germanium to make transistors. It is also used to make other electrical components such as rectifiers, thermistors and photoconductors. Indium can be used to make mirrors that are as reflective as silver mirrors but do not tarnish as quickly. Indium is also used to make low melting alloys. An alloy of 24% indium and 76% gallium is a liquid at room temperature.