Peter Grünwald heads the machine learning group at CWI in Amsterdam, the Netherlands. He is also full professor of Statistical Learning at the mathematical institute of Leiden University. Currently the President of the Association for Computational Learning, the organization running COLT, the world’s prime annual conference on machine learning theory, he was co-program chair of COLT in 2015 and also chaired UAI – another top ML conference – in 2010/2011. Apart from publishing at ML venues like NIPS, COLT and UAI, he also regularly contributes to statistics journals such as the Annals of Statistics. He is the author of the book The Minimum Description Length Principle, (MIT Press, 2007; see here for an up-to-date (2020), much shorter introduction), which has become the standard reference for the MDL approach to learning. In 2010 he was co-awarded the Van Dantzig prize, the highest Dutch award in statistics and operations research. He received NWO VIDI (2005), VICI (2010) and TOP-1 (2016) grants.