Hello! May I ask for a little assistance in filling in the gaps of my understanding? :S I understand that the current large scale structure of the Universe is thought to be the result of early fluctuations in density which have been stretched out in the expansion of the Universe. I am a bit muddled as to why you can model these density fluctuations (CDM model) as Gaussian at 'decoupling'. 1. If decoupling is the moment in recombination at which Compton scattering became less than the expansion of the universe, how does that make it Gaussian? Is it just based on the fact that the photons stopped interactions with matter at this point, such that there would be a spread of velocities? Any hints would be very much appreciated!