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The structure formation in the universe is a subject of a great interest since last century and it is directly linked to the evolution of the universe. During this time different models have been proposed and nowadays the paradigm is that quantum density fluctuations grew since the inflationary epoch until they become non-linear and are virialized. These initial fluctuations are described by the Harrison Zeldovich power spectra which is modified by some physical effects until the separation between radiation and matter at the moment of recombination (z = 1100). From that moment on only gravity affects these fluctuations increasing their amplitude but not modifying the shape of power spectra. The radiation escaping at recombination which is observed now reflects the fluctuations at that moment and it allows us to determine that the cold dark matter (CDM) is necessary to explain the acceleration of the growth of the barionic fluctuations. The consideration of the CDM, that produces the bottom-up formation of the structures, and the accelerated expansion of the universe leads to the ΛCDM model.