Pierre Soulages has never depicted light but has transformed it into pictorial material, a unique artistic approach that has fascinated several scientists at the Ecole Polytechnique Fédérale de Lausanne. Thanks to high-tech devices, these physicists have recently experimented with the phenomena of interaction between matter and light involved in Soulages' paintings and offer a fascinating perception of them. Through previously unseen images and interviews, the viewer will discover the fruitful dialogue that develops between art and science.