  The origins of planets, and perhaps life itself, is intrinsically linked to
the chemistry of planet formation. In this chapter we will attempt to explore
the chemistry of planet-forming disks from the perspective of knowledge gained
from decades of solar system study, combined with our rapidly growing knowledge
of extra-solar protoplanetary disks. Our aim is not to provide a comprehensive
survey of the literature, but rather to present the chemical and physical tools
that are used to explore chemical evolution during the earliest stages of
planet formation. We include a discussion of observational constraints from our
solar system and extra-solar disks, thermodynamic equilibrium and chemical
kinetics, and the physical prescriptions for various important aspects
(X-ray/UV irradiation, thermal structure, molecular adsorption/desorption, ..)
that are used in current models. The chapter is aimed for young researchers.
