Historical time-line of the cosmic microwave background radiation showing the start of photon/nuclei combination, the surface of last scattering (SoLS), and the epoch of reionization due to early star formation. The times are represented in years (to the right) and redshift (to the left). Primary anisotropies are collectively attributed to the early effects at the last scattering surface and the large scale Sachs-Wolfe effect. Secondary anisotropies arise from path integration effects, reionization smearing, and higher order interactions with the evolving nonlinear structures at relatively low redshifts (http://relativity.livingreviews.org/open?pubNo=lrr-2001-2&page=articlesu9.html).