Final answer:
The early universe matter that formed galaxies and stars consisted of luminous and dark matter with slight non-uniformities. Vibrations from the Big Bang concentrated matter in high-density areas, which over time merged to form larger structures, such as galaxy clusters and superclusters.
Step-by-step explanation:
The matter in the early universe that eventually condensed into galaxies and then into stars primarily consisted of luminous and dark matter. In the beginning, this matter was nearly uniform but had slight variations which led to the formation of structures like galaxies and voids. As the universe cooled, those slight over-densities became the sites of galaxy formation.
During the Big Bang, the universe was filled with a hot mixture of particles and energy. Sound-wave-like vibrations in this 'soup' created regions of higher density, framing the earliest structure of the cosmos. Over time, these small clumps of matter merged to form larger structures, such as stars, galaxy clusters, and superclusters. As galaxies like the Milky Way formed, they continued to grow by accumulating material and merging with other galaxies.
Research indicates that supermassive black holes and matter in galaxies formed concurrently. The cosmic microwave background (CMB) provides evidence for these initial fluctuations. Our current understanding of the universe's composition includes ordinary matter, dark matter, and dark energy, which all played roles in the development of cosmic structures.