The Swiss Light Source (SLS) has been operational now for nearly two decades. In this period, it has spearheaded groundbreaking research in biomedicine, engineering and the natural sciences, thanks in large part to the excellent performance of the underpinning electron accelerator and storage ring complex. In addition, it has led the world in industrial exploitation, particularly by the pharmaceutical sector, and spawned numerous new companies, including one of the most successful Swiss technology spinoffs, Dectris. For much of this time, the SLS was a benchmark with regards to how closely its performance matched the theoretical limits deﬁned by its machine parameters. However, with the advent of the next generation of synchrotron light sources, called diffraction-limited storage-rings, that yield an emittance and brightness improved by up to two orders of magnitude, it has become imperative to upgrade the SLS (called SLS 2.0) in like manner. It is planned to upgrade the machine in 2023/2024 with a planned improvement in performance of a factor of 40, and return to regular user operation in 2025.