The physical contact between objects plays a crucial role in the dynamics of physical systems.Two examples are granular matter, which can undergo transitions from a state of flow to one of arrested motion (jamming), and the ubiquitous friction between all kinds of surfaces.Fluorescence spectroscopy is an ideal tool to observe such contacts on the sub-micrometer length scale because it is non-invasive, and with the proper experiment design, allows to look through objects and to observe interfaces that cannot be addressed with scanning probe methods.