 Here's a projection of the celestial dome as seen by the Wilkinson Microwave Anisotropy probe factoring out all local and local group motion. The mapping preserved the relative sizes of the surface objects. The key observation is that the light fits the black body radiation curve perfectly. This gives us the temperature of the radiation today. It is 2.725 degrees. We know that at decoupling it was 3,000 degrees. So the temperature has been reduced by a factor of 1,100. So the universe has expanded by a factor of 1,100 times since decoupling. The black body radiation formula also gives us the number density of CMP photons. There are over 400 million of them in every cubic meter of space throughout the cosmos. This is a thousand times more than all the photons from all the starlight ever created by all the stars and all the galaxies for all the billions of years that stars have been shining. The CMP redshift tells us that the light we see now was only 42 million light-years away from our location when it was emitted. It traveled for just under 13.8 billion years to reach us and its starting location is now 46.5 billion light-years away, making the diameter of the visible universe 93 billion light-years. The Planck satellite measurements detected small amounts of temperature deviation. The image uses color to show variations from the average with blue for minus 200 millionths of a degree through green and yellow to red, which represents plus 200 millionths of a degree. That temperature deviation comes to one part in 100,000. These temperature deviations come from equally small mass density deviations in the plasma at the time of decoupling. We see large structures, small, even tiny structures, and giant structures. We even see structures within structures at every scale. In other words, they're quite fractal. These differences in the CMB are what led to large-scale structures such as galaxy clusters, filaments, and voids that we see today. For example, a very tiny spot of red on the surface of last scattering, representing a small decrease in mass density in that region, will have expanded 1,100 times to the size of the coma cluster today.