Ernesto Estrada is full CSIC Research Professor at the Institute of Cross-Disciplinary Physics and Complex Systems (IFISC). Estrada has been a major contributor in the study of complex networks, where he has developed several approaches to investigate the network topology and dynamics. An index introduced by him in 1999 to characterize the degree of protein folding, and then generalized to the study of complex networks in 2005, is nowadays widely known as the Estrada index of a graph or network. His work is more on the mathematical side of the study of networks, although he is also interested in its applications to real-world complex systems. He is the proponent of approaches such as the 'subgraph centrality', 'communicability', 'spectral scaling','d-path Laplacians', 'hubs-biased Laplacians', among others. Estrada is also known in the area of mathematical chemistry, in particular for the development and use of molecular descriptors based on the use of Graph Theory. In recent years he has developed mathematical approaches for the Hückel method or tight binding model, such as for 'graph energy', 'density matrix', 'quantum molecular interference' in molecular electronics, among others. The last work is in collaboration with Nobel Prize in Chemistry Roald Hoffmann. For his works Estrada has received many distinctions such as being elected as Fellow of the Society of Industrial and Applied Mathematics, Member of the Academia Europeae, Fellow of the Institute of Mathematics and its Applications, member of the Latin American Academy of Sciences. He also received the Wolfson Research Merit Award of the Royal Society of London. In total he has published more than 230 paper and two textbooks, he is member of the editorial board of several prestigious journals and it is Editor in Chief of the Journal of Complex Networks, published by Oxford University Press.