All known atomic nuclei and therefore almost all visible matter consist of protons and neutrons, yet many of the properties of these omnipresent natural building blocks remain unknown. As an uncharged particle, the neutron in particular resists many types of measurement and 90 years after its discovery there are still many unanswered questions regarding its size and lifetime, among other things. The neutron consists of three quarks which whirl around inside it, held together by gluons.