I will describe our attempts to construct generative models of cellular metabolic fluxes through statistical inference from empirical data. I will try to clarify the technical difficulties to be overcome and motivate why this approach is worth the effort. Concerning results, I mostly focus on (i) dynamical views of phenotypic diversity, (ii) the existence of a testable hard bound relating fitness to (inferred) heterogeneity, and (iii) the possibility to identify an `objective function’ of metabolic activity. If time permits, I will finally present some preliminary results where inverse modeling is applied to the reconstruction of inter-cellular interactions in populations of cancer cells.