  The aim of the chapter is to summarize our understanding of the compositional
distribution across the different reservoirs of small bodies (main belt
asteroids, giant planet trojans, irregular satellites of the giant planets,
TNOs, comets). We then use this information to i) discuss current dynamical
models (Nice and Grand Tack models), ii) mention possible caveats in these
models if any, and iii) draw a preliminary version of the primordial
compositional gradient across the solar system before planetary migrations
occured. Note that the composition of both planetary satellites (the regular
ones) and that of the transient populations (NEOs, centaurs) is not discussed
here. We strictly focus on the composition of the main reservoirs of small
bodies. The manuscript's objective is to provide a global and synthetic view of
small bodies' compositions rather than a very detailed one, for specific
reviews regarding the composition of small bodies, see papers by Burbine (2014)
for asteroids, Emery et al. (2015) for Jupiter trojans, Mumma and Charnley
(2011) for comets, and Brown (2012) for KBOs.
