“ Because of the large variation in timescales and concentrations, developing a whole-cell model that treats metabolism, genetic information processes, and growth can, at the moment, only be achieved by hybrid stochastic and deterministic simulations. Kinetics of the essential metabolic network (Breuer et al., 2019) are handled deterministically via ordinary differential equations (ODEs), and the kinetics of the genetic information processes are handled with stochastic simulations.”

This reminds me of a description of how different levels of realism were chosen and combined to simulate a whole person in a Greg Egan science fiction book (Permutation City - I think). IIRC there is a scene where a character spends some time in the shower knowing that the partial differential equations for simulation of the water will be driving up the costs of running the simulation.

Edit: added the bit about Greg Egan.