In this lesson we'll explain why there is structure and "clumpyness" in the universe. In other words, why there is more stuff here than over there. Now, if all of the distribution of matter and energy in the universe was initially completely uniform (meaning homogenous and isotropic), then galaxies, stars, and people would have never formed. Non-uniform density would never arise in such a universe. But due to the time-energy uncertainty principle, the distribution of matter and energy must have had been randomly distributed throughout space at the beginning of the universe. Since the distribution was truly random, there would always be regions of space with slight more matter and energy than other. These slight non-uniformities ("imprinted" by the uncertainty principle) in matter and energy density throughout space near the beginning of the universe is the origin of the slight non-uniformities that we see in the CMBR.