In the 1970s numerous studies showed that tiny deviations from isotropy in the CMB could result from events in the early universe. Harrison, Peebles and Yu, and Zel'dovich realized that the early universe would require quantum inhomogeneities that would result in temperature anisotropy at the level of 10 or 10. Rashid Sunyaev calculated the observable imprint that these inhomogeneities would have on the cosmic microwave background.