Iron-based superconductors possess an unusual property known as electronic nematicity, in which electrons spontaneously choose a preferred direction. The nematic state and its fluctuations are thought to be related to the superconductivity, but much remains unknown. We propose to use pair distribution function analysis of neutron scattering data to study short-range structural distortions arising from nematic fluctuations in two archetypal families of iron-based superconductors, BaFe2(As,P)2 and Fe(Te,Se). The results will provide rich information about nematic fluctuations, including their extent in temperature and composition space, their length scale, and their magnitude.