Tristability in the intracellular GRN controlling the differentiation of ICM cells into Epi and PrE. (A and B) Bifurcation diagrams of the model defined by Eqs. 1–4 as a function of parameter Fp, which represents the extracellular concentration of Fgf4. Three stable steady states coexist in the (0.0575,0.0663) interval. (C) Time evolutions in the (Gata6, Nanog) phase space from different initial conditions, showing the basins of attraction of the three stable steady states. Simulations correspond to Fp = 0.06, which value belongs to the domain of tristability. Parameter values are given in Table S1. (D) Sensitivity analysis of tristability. For each parameter listed, the bar indicates the range of relative variation—expressed as a change in percentage in the parameter value with respect to its default value—in which tristability is maintained. Default parameter values are listed in Table S1. Bifurcation diagrams were generated with AUTO (45).