Modeling the Plasma Epoch

 CMB is a sample of the density structure on a shell cut through the 400,000 year old Universe.

Theory of gravitational oscillations in a plasma is easy!

For given initial conditions the evolution of in-homogeneity ("lumpiness") in the primordial soup can be accurately calculated.
Prediction: CMB should be a Gaussian random pattern whose total information content is encoded in it's angular power spectrum.
The way in which the plasma oscillates is determined by the types of material it contains