  Mean motion resonances play a fundamental role in the dynamics of the small
bodies of the Solar System. The last decades of the 20th century gave us a
detailed description of the dynamics as well as the process of capture of small
bodies in coplanar or small inclination resonant orbits. More recently,
semianalytical or numerical methods allowed us to explore the behavior of
resonant motions for arbitrary inclination orbits. The emerging dynamics is
very rich, including large orbital changes due to secular effects inside mean
motion resonances. The process of capture in highly inclined or retrograde
resonant orbits was addressed showing that the capture in retrograde resonances
is more efficient than in direct ones. A new terminology appeared in order to
characterize the properties of the resonances. Numerical explorations in the
transneptunian region showed the relevance and the particular dynamics of the
exterior resonances with Neptune which can account for some of the known high
perihelion orbits in the scattered disk. Moreover, several asteroids evolving
in resonance with planets other than Jupiter or Neptune were found and a large
number of asteroids in three-body resonances were identified.
