Modularity map of the network of human cell differentiation SUPPLEMENTARY INFORMATION IV. ADDITIONAL INFORMATION FOR NHCD 21 FIGURE 5 provides an alternative representation of the NHCD. Different cell types appearing as bifurcation points of the network are stacked along the vertical axis. In SI-Fig. 5a the horizontal axis corresponds to the shortest path ℓ$_{N}$ 1 calculated from node N 1, the fertilized egg, to any given node, while in SI-Fig. 5b the same network is shown as a function of the node appearance time T$_{a}$ . The links emerging from each cell type follow a bifurcation pattern ending up at the right side with k − 1 branches, each one of them representing one of the more specialized cell types. Red nodes correspond to the surviving cell types, and they preferentially appear at later times, while the non-surviving cell types, the blue nodes, emerge during the early stages of the process. The color of the edges corresponds to one of the 19 functional groups identified in Table I as given in Fig. 1. Links that generate loops are plotted in red. Figure 5b contains the same information as Fig. 5a but we plot each cell type according to its time of appearance rather than as a function of the chemical distance to N 1, as in Fig. 5a. The white and yellow alternating vertical stripes divide the time axis in intervals in days. The branches have been extended so that each cell appears only in the corresponding interval. Colors and labels are the same as in Fig. 5a. The catalog presented in Ref. [6] reports 407 distinct cell types in a healthy adult human body, all of which can be identified in our network representation. Most of them occupy the end points of the 529 branches in Figs. 1 and 5. Therefore, not all tree leaves (branch endpoints) correspond to cell types in born humans. The average shortest path calculated from all cell types to N 1 is 〈 ℓ$_{N}$ 1 〉 = 10 . 93, as expected from the large concentration of links in the interval 8 ≤ ℓ ≤ 13 (Fig. 5a). FIGURE 6 shows the full modular structure of the NHCD as detected by the box- covering algorithm at different length scales. A detail of this process is represented in Fig. 2 in the main text. A list containing the nodes belonging to each module at a given ℓ is