  Chondritic meteorites constitute the most ancient rock record available in
the laboratory to study the formation of the solar system and its planets.
Detailed investigations of their mineralogy, petrography, chemistry and
isotopic composition and comparison with other primitive solar system samples
such as cometary dust particles have allowed through the years to decipher the
conditions of formation of their individual components thought to have once
been free-floating pieces of dust and rocks in the early solar nebula. When put
in the context of astrophysical models of young stellar objects, chondritic
meteorites and cometary dust bring essential insights on the astrophysical
conditions prevailing in the very first stages of the solar system. Several
exemples are shown in this chapter, which include (1) high temperature
processes and the formation of chondrules and refractory inclusions, (2) oxygen
isotopes and their bearing on photochemistry and large scale geochemical
reservoirs in the nebula, (3) organosynthesis and cold cloud chemistry recorded
by organic matter and hydrogen isotopes, (4) irradiation of solids by flares
from the young Sun and finally (5) large scale transport and mixing of material
evidenced in chondritic interplanetary dust particles and samples returned from
comet Wild2 by the Stardust mission.
