Centralities of a target protein in a toy model. Illustration of degree (D), eigenvector score (EC), topological importance up to one step (TI1), betweenness (B) and closeness (C). The black protein has three gray neighbors: D = 1+1+1 = 3. When the importance of direct connections is weighted, the black node is ranked 2nd (EC = 0.925) since two gray nodes out of three are highly connected (EC = 1.000 and EC = 0.676). We also know the white neighbors of its gray neighbors: TI1 = 1 + 0.25 + 0.33 = 1.58. This latter index defines the relative importance of the target protein (in black), in comparison to the "clouds" of (white) proteins connected to its direct (gray) neighbors (since it is computed up to 1 step, TI1). The relative importance of the black protein at the whole network level depends on its mediator-role in connecting every other pair of proteins (B = 19), or is measured in terms of average proximity to the others (C = 0.615). Because of its barycentric position, the black node ranks 1st both in terms of betweenness and closeness.