  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.
