Illustration of the US chemist John B Fenn (1917-2010). Fenn is best known for his development of electrospray ionisation for mass spectrometry. Mass spectrometry uses strong magnetic and electric fields to separate the components of a sample by mass and charge. This requires the sample to be in the form of a gas of ions. Before electrospray ionisation this wasnt possible for large molecules such as proteins as the ionisation techniques degraded them. Fenn received a share of the 2002 Nobel Prize in Chemistry, along with Koichi Tanaka and Kurt Wuthrich, for this work.