Hi I know that this question has been answered in other threads, but those threads seemed to be closed now, and what I am looking for is a real "for beginner - real dummies" type answer. I understand that there are ripples in the background microwave radiation. The text book (OU) I am reading at the moment, then goes on to start talking about variations in the density of matter. So my first question is (please excuse the basic level of these questions) is there assumed to be a connection between the variations in matter density and CMB? If so, why is that? Do the surveys of the CMB reflect the distribution of galaxies in the universe? Also can any one explain in really simple terms, how Fourier series and Fourier transforms get involved with all of this? I kind of understand what Fourier series are. Is there any decent literature that someone could point me in the direction of in order to better understand this topic? I generally like the Open University and have had little but praise for them in the past, but the four pages related to this topic are among the most incomprehensible I have ever come across. Thanks in advance for any help. Cheers and seasons greetings to all you.