  We take up the challenge of designing realistic computational models of large
interacting cell populations. The goal is essentially to bring Gillespie's
celebrated stochastic methodology to the level of an interacting population of
cells. Specifically, we are interested in how the gold standard of single cell
computational modeling, here taken to be spatial stochastic reaction-diffusion
models, may be efficiently coupled with a similar approach at the cell
population level.
  Concretely, we target a recently proposed set of pathways for pattern
formation involving Notch-Delta signaling mechanisms. These involve
cell-to-cell communication as mediated both via direct membrane contact sites
as well as via cellular protrusions. We explain how to simulate the process in
growing tissue using a multilevel approach and we discuss implications for
future development of the associated computational methods.
