Exploring the unknown: The work of Louis Nirenberg on partial differential equations

They were for a long time restricted only to the study of natural phenomena or questions pertaining to geometry, before becoming over the course of time, and especially in the last century, a eld in itself. The second half of the XXth century was the \golden age" of the exploration of partial dierential equations from a theoretical perspective. The mathematical work of Louis Nirenberg since the early 1950s has to a large extent contributed to the growth of this fundamental area of human knowledge. The name Nirenberg is associated with many of the milestones in the study of PDEs. The award of the Abel Prize to Louis Nirenberg marks a special occasion for us to revisit the development of the eld of PDEs and the work of one of the main actors of its exploration.