In a new Ideas and Perspectives paper in Ecology Letters, Bogdziewicz et al. review the most relevant proximate drivers of masting and outline a research agenda that takes the biology of masting from a largely observational field of ecology to one rooted in mechanistic understanding. They divide the experimental framework into three main processes: resource dynamics, pollen limitation, and genetic and hormonal regulation, and illustrate how specific predictions about proximate mechanisms can be tested, highlighting the few successful experiments as examples.