Miguel Leal, Ole Seehausen and Blake Matthews published an opinion paper in TREE about the ecology and evolution of stoichiometric phenotypes. The stoichiometric or elemental phenotype is defined by the elemental composition, assimilation, allocation, or excretion of an individual, measured as its elemental content or ratios between elements. Miguel et al discuss how variation in the elemental phenotype among individuals can affect individual fitness variation and how the evolution of elemental phenotype can influence ecosystem processes. They make suggestions for a research program to address these questions. This research might improve our ability to predict how organisms adapt to changing environmental conditions and may contribute to our understanding of eco-evolutionary feedbacks.