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. A previous chair of top ML conferences 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, 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. His research currently focuses on tests and confidence sequences that remain safe under optional stopping - with as central underlying concept the E-value, which has a very strong BFF flavour.