Hot Topics in Contemporary Crystallography by Croatian Association of Crystallographers The humanity is these days just a bit more than a century away from the first structural studies based on the diffraction of X-rays on crystals. Over this relatively short period of time, the level of complexity that the crystallographers are capable of examining has gradually multiplied literally by millions. In particular, over the last decade or so, we are witnessing a remarkable advance in experimental methods and theoretical approaches in crystallography which are putting this scientific branch of ours to the front lines of not only structural chemistry, but of natural sciences in general. In order to review and tackle these fascinating recent achievements and developments, we in Croatian Association of Crystallography, have, three years ago, developed the concept and launched the first edition of Hot Topics in Contemporary Crystallography – a high level workshop intended to the utterly ambitious PhD students and postdocs, as well as to the young crystallographers in the early stages of their autonomous carriers, conducting their research within the broad spectrum of disciplines and sub disciplines related to crystallography. It was held from May 10th to 15th, 2014 in Šibenik, Croatia and it was a central event to mark the UN proclaimed International year of crystallography in Croatia. The workshop was a great success – we had 27 students and 6 lecturers from 15 countries. All students obtained bursaries which partly or entirely covered their onsite expenses thanks to the generous support from IUCr, ECA and a long list of commercial sponsors. There was no registration fee for this event. Six “hot topics” were tackled: Hot topics in macromolecular crystallography (by prof. dr. Elspeth Garman, University of Oxford, UK), The whole is more than the sum of its parts (by prof. dr. Hans-Beat Bürgi, University of Bern, Switzerland), Charge density (by prof. dr. Dietmar Stalke, University of Göttingen, Germany), Absolute structure and absolute configuration (by prof. dr. Howard Flack, University of Geneve, Switzerland), Twinning in crystallography (by dr. Regine Herbst-Irmer, University of Göttingen, Germany), and Advanced solutions from the Cambridge Structural Database (by Pete Wood from Cambridge Crystallographic Data Centre, UK). The second edition of the Hot Topics in Contemporary Crystallography – HTCC2017, was held in Poreč, one of the jewels of the Croatian Adriatic, from Apr. 22nd to 26th, 2017. The generous support of Bruker AXS, Dectris, ECA and MiTeGen enabled us to provide nine bursaries for students. The workshop gathered 20 students and nine lecturers and three truly hot topics covered were: Dynamic crystallography (by prof. dr. Samar Hasnain from the University of Liverpool, prof. dr. Henry Chapman from the University of Hamburg and prof. dr. Ilme Shlichting from the Max Planck Institute), crystallography under non-ambient conditions (by prof. dr. Simon Parsons from the University of Edinburgh and dr. Martin Adam from Bruker AXS), and charge density studies (by prof. dr. Piero Macchi from the University of Bern, dr. Christian Jelsch from the University of Lorraine and dr. Krešimir Molčanov from the Ruđer Bošković Institute). The role of cutting edge detectors in the contemporary X-ray experiments was discussed by dr. Dubravka Šišak Jung from Dectris Ltd.).