  A fair and complete accounting of cosmic baryons now appears possible,
because most of them are in states which are either directly observable or
reliably constrained by indirect arguments. More than three-quarters of the
baryons are probably in hot ionized gas clustering, along with galaxies and
dark matter, in the cosmic web. The rest are in galaxies, roughly equally
distributed between old stellar populations and star-forming disk populations;
within the latter, mass is distributed about equally between stars and (mostly
neutral and molecular) gas. The total amount of matter agrees with that
required for concordance of cosmic light element abundances with Standard Big
Bang Nucleosynthesis, a neat result inviting deeper studies of baryon
evolution.
