We develop multiscale models that couple cell-cell communication with cell-internal gene regulatory network dynamics to study cell fate decision-making from a dynamical systems perspective. In JuliaLang, we model cell-cell communication as a Poisson process, and cell-internal dynamics with nonlinear ordinary differential equations, taking advantage of the power of DifferentialEquations.jl. We show that subtle changes in cell-cell communication lead to dramatic changes in cell fate distributions.