The MATLAS project explores the surroundings of a complete sample of nearby massive early-type galaxies with multi-colour deep optical images obtained at the Canada-France Hawaii Telescope. The observing and data reduction techniques ensured the detection of extended low-surface-brightness (LSB) structures, while the high image quality allowed us to identify associated compact objects such as star clusters. A number of scientific topics are addressed with this data-set that are briefly presented in this review: the study of foreground Galactic cirrus at high spatial resolution, telling us about the ISM structure; the characterisation of collisional debris around the galaxies (streams, tails, shells, stellar halos), giving hints on their past merger history; the distribution of dwarf galaxy satellites, including the ultra-diffuse ones, together with their globular cluster population, which are additional tracers of the formation and mass assembly of galaxies.