Phenotypic heterogeneity – physical diversity amongst genetically identical individuals exposed to the same environmental conditions – is a phenomenon that has caught the interest of biologists for decades. Although recent technological advances have revolutionised our understanding of the mechanistic bases of phenotypic heterogeneity, its adaptive significance and associated biological function(s) remain largely obscure. Two hypotheses have been proffered: (i) the “bet hedging” hypothesis, which postulates that phenotypic heterogeneity is a risk-spreading strategy facilitating population survival in uncertain environments, and (ii) the “division of labour” hypothesis, which proposes that phenotypic heterogeneity can increase population efficiency by partitioning labour (or resources). However, despite great interest in this area, empirical evidence for the biological significance of phenotypic heterogeneity is severely lacking. Here, I propose a series of experiments that combine molecular genetics, state of the art single cell analysis techniques and metabolomics to directly test the biological significance of a recently characterised example of phenotypic heterogeneity: ON/OFF colanic acid capsule expression in the bacterial model system Pseudomonas fluorescens SBW25. By providing a direct, experimental test of hitherto theoretical hypotheses, the proposed experiments have the potential to provide some of the first empirical insight into why phenotypic heterogeneity is such a widespread phenomenon. In addition to being of academic interest, our results will have direct relevance for industries involved in the management of infectious microbes (public health, veterinary science and agriculture) and the use of microbes in product manufacture (biotechnology) and toxin breakdown (bioremediation).