  This chapter reviews accretion models for Kuiper belt objects (KBOs),
discussing in particular the compatibility of the observed properties of the
KBO population with the streaming instability paradigm. Then it discusses how
the dynamical structure of the KBO population, including the formation of its 5
sub-components (cold, hot, resonant, scattered and fossilized), can be
quantitatively understood in the framewok of the giant planet instability. We
also establish the connections between the KBO population and the Trojans of
Jupiter and Neptune, the irregular satellites of all giant planets, the Oort
cloud and the D-type main belt asteroids. Finally, we discuss the collisional
evolution of the KBO population, arguing that the current size-frequency
distribution below 100~km in size has been achieved as a collisional
equilibrium in a few tens of My inside the original massive trans-Neptunain
disk, possibly with the exception of the cold population sub-component.
