Population growth is fundamental to microbiology, underpinning processes from biofilm formation to industrial fermentation. Yet one of its most central features – the relationship between per-capita growth and population density – remains surprisingly contentious. Recent high-profile analyses of empirical time series have reported that sublinear density dependence, in which growth rates decline primarily at low densities, is widespread in plants, animals, and microbes. However, this pattern is difficult to reconcile with resource-dependent growth theory, which instead predicts superlinear density dependence, where growth rates decline most rapidly at high densities. In this talk, I will show how microbial systems provide an ideal experimental platform for resolving this tension between the data and the theory. One reason why the shape of density dependence is still debated is that manipulating densities and measuring growth rates isn’t feasible in most systems. We therefore flipped the problem by manipulating growth rates and measuring resulting densities in a technique we call “Growth-Density Inversion”. To do this we grew Escherichia coli populations in chemostats at different dilution rates and quantified equilibrium densities. These experiments, together with an independently parameterised consumer-resource model based on Monod kinetics, demonstrate that superlinear density dependence emerges naturally in simple resource-limited systems. We then performed a series of batch culture assays to show how more complex growth dynamics (e.g. multiple-resource co-limitation, diauxic growth) can produce more complex density dependence with both super- and sublinear regions. These findings highlight how microbial experiments can uncover general principles governing population regulation across biological systems.