A team of physicists at the Institut Lumière Matière (CNRS/Université Claude Bernard Lyon 1), in collaboration with the Cancer Research Center of Lyon (CNRS/INSERM/ Université Claude Bernard Lyon 1/Centre Léon Bérard/Hospices civils de Lyon), has demonstrated the potential of an imaging technique based only on the physical properties of tumors. It can differentiate populations of malignant cells and monitor how effective an anticancer treatment is. These results, published in Physical Review Letters on January 8, 2019, should help in the design of new therapeutic molecules and in the personalization of treatments.