Schematic representation of the identifiability phenomenon. (A) The dynamics of the nodes of three different structural networks (i, ii, and iii) are recorded (“test”). (B) The coordination between all pairs of nodes is quantified, and the corresponding functional networks are obtained. In the figure, we plot the matrices containing the weights of the links of the functional networks. Next, a second measurement is carried out (“re-test”), and the corresponding functional network is compared with the previous ones. (C) All test (rows) and re-test (columns) functional networks of each structure (i,ii and iii) are compared by pairs. The elements of the matrix contain the correlations (p) between each pair of functional networks. Identifiable systems are those whose diagonal has much higher values than the off-diagonal ones (first matrix of the plot). On the contrary, when all values are low (second matrix) or high (third matrix), the identification is not possible.