We present our current knowledge of the solar chemical composition based on the recent significant
downward revision of the solar photospheric abundances of the most abundant metals very recently
reviewed in detail by Asplund et al. (2005a). These new solar abundances result from the use of a
3D hydrodynamical model of the solar atmosphere instead of the classical 1D hydrostatic models,
accounting for departures from LTE, and improved atomic and molecular data. With
these abundances, the new solar metallicity, Z, and Z/X, decrease to Z = 0.012 and Z/X = 0.0165 respectively, almost a factor of 2 lower than earlier widely used values. While resolving a number of
longstanding problems, the new 3D-based solar photospheric composition also poses serious challenges
for the standard solar model.