Metrics & MoreArticle Recommendations J uan JoséSaénz, also known to his colleagues and many friends as "Juanjo" or "Mole", Ikerbasque Professor at the Donostia International Physics Center (DIPC), left us unexpectedly and far too soon on the morning of March 22. The sad news was received as an unbelievable shock by his beloved family and by dozens of his many good friends all over the globe. It is still hard to believe that we will not see again Juanjo's eternal smile (with an unlit cigarette hanging from the corner of his mouth), feel his vivacity and enthusiasm, enjoy his endless supply of encouragement, support, and honesty, and benefit from his powerful stream of ingenious ideas in a wide variety of fronts. We must learn to accept that we have lost, not only one of the brightest minds in our community, but also a friend always ready to lend a hand, willing to have a chat that would usually end up in discussion on unforeseen scientific topics. A theoretician by training, he was one of those scientists with insatiable curiosity about the basics of Physics, but also about its implications in other fields, such as Chemistry and Biology. His students (Torres, Garcı ́a-Martı ́n, Froufe-Peŕez, and many others) already miss him profoundly as a caring mentor, almost a father, both scientifically and personally.Born in Madrid, he graduated in Physics from the Universidad Autońoma de Madrid (UAM), where he completed a Ph.D. in 1987 on the stability of small metallic clusters. Thereafter, he moved as a postdoctoral fellow to IBM Zurich, where he worked with Heinrich Rohrer on the theory of scanning tunneling microscopy (STM) and magnetic force microscopy. He returned to UAM in 1989, where he became Professor and worked on the quantization of conductance in metallic contacts, wave transport in disordered media, probe microscopies, and optical forces. After many interim summer stays and a sabbatical year at DIPC, Juanjo moved permanently to San Sebastian in 2015 and focused on novel phenomena in photonics, including