All biological systems function by molecules interacting, however, it is often challenging to determine what molecules interact with each other and what effect the interaction has on their structure and function. In this talk consideration will be given to how spectroscopy and chomatography can be used to determine whether molecules interact and how that affects their behaviours. Applications to how the molecules in plant-based milks assemble; how peptides and proteins interact with membranes; and how extra cellular vesicles interact withtheir environments will be considered. A wide range of spectroscopic techniques can give complementary clues aboutmolecules assembly. This talk will include consideration of the polarised light spectroscopies of circular and linear dichroism (in electronic and vibrational spectroscopy) and polarised light emission and how chromatography can complement spectroscopy. Illustrations will include wavelength scanning circularly polarised luminescence (CPL), linearly polarised luminescence (LPL), easy to measure fluorescence polarisation anisotropy (FPA), as well as fluorescence detected circular dichroism and linear dichroism.