  The interaction between dark matter and dark energy can be incorporated into
field theory models of dark energy that have proved successful in alleviating
the coincidence problem. We review recent advances in this field, including new
models and constraints from different astronomical data sets. We show that
interactions are allowed by observations and can reduce the current tensions
among different measurements of cosmological parameters. We extend our
discussion to include constraints from non-linear effects and results from
cosmological simulations. Finally, we discuss forthcoming multi-messenger data
from current and future observational facilities that will help to improve our
understanding of the interactions within the dark sector.
