The CECAM community mourns Herman Berendsen, who passed away on October 7 2019. Prof. Berendsen was a pioneer of atomistic and molecular simulations, constantly pushing the field beyond its limits and with a keen interest in method development motivated by new and challenging application. His role in establishing simulations as a key tool in the study of biomolecules cannot be overemphasised and his outstanding contributions and leadership have been instrumental in shaping our science and the spirit of our community. 
Throughout his long and distinguished career, Prof. Berendsen has maintained a strong and fruitful relationship with CECAM. His generous and key role in establishing our institution as a focal point of simulation in Europe and in the world is reflected in the organisation of seminal workshops that brought new communities to CECAM and opened new areas of investigation. Of the 13 CECAM workshops organised or co-organised by Prof. Berendsen since 1972 we mention here “MD and MC of water” (1972) and the outstanding “Models for Protein Dynamics” (1976). In recognition of his exceptional contributions, Herman Berendsen was awarded the 2013 Berni J. Alder CECAM prize jointly with Prof. Jean-Pierre Hansen. 
To better honour Prof. Brendsen’s memory, we provide here access to three documents. The first two documents have been written by his colleague and friend Wilfred van Gunsteren on the occasion of Herman’s retirement from his chair at the University of Groningen in 1999  and, more recently,  to celebrate his 85thbirthday. These papers contain a complete and insightful description of Prof. Berensen’s role in the community and of his scientific contributions, ranging from the iterative SHAKE algorithm for implementing constrained molecular dynamics, to the SPC model for water; from pioneering ideas on calculation of hydration free energy, to density matrix propagation for hybrid quantum/classical simulations.
We also include an excerpt from a recent email exchange between him and Giovanni Ciccotti in which Herman himself describes his background as an experimentalist and how he became interested in simulations (all links to files are signalled in red above).
We feel that these documents provide a vivid and interesting portrait of Prof. Berendsen’s scientific curiosity, of his remarkable scope and of his most important contributions to molecular simulation. We are very grateful to Wilfred van Gunsteren  and Giovanni Ciccotti for sharing them with us and allowing us to (re)publish them with this short “in memoriam”. We hope that they will give an opportunity to us all to remember or get to know this master of simulations.