The universe began about 13.8 billion years ago with the Big Bang, an explosive event that marked the beginning of space and time. At its start, the universe was incredibly hot and dense. Within the first few minutes, protons and neutrons formed from the primordial quark-gluon plasma and began to combine into hydrogen and helium atoms.
Over the next several hundred thousand years, the universe cooled sufficiently for electrons to combine with nuclei, forming neutral atoms. This phase is known as "recombination," and it allowed light to travel freely through space, creating the Cosmic Microwave Background radiation that we can still observe today.
As millions of years passed, gravity pulled the initially homogenous primordial gas into clumps, forming the first stars and galaxies. These massive structures began the cycle of stellar evolution, where stars fuse elements in their cores, contributing to the chemical enrichment of the universe.
Galaxies, each containing billions of stars, clumped together into groups, clusters, and superclusters, driven by gravitational attraction. Some galaxies collided and merged, shaping the large-scale structure of the universe as seen today.
Around 9 billion years after the Big Bang, our Solar System formed within a molecular cloud in the Milky Way galaxy. The Sun and planets coalesced from the gravitational collapse of a part of this cloud.
Currently, the universe is not only expanding, but this expansion is accelerating due to a mysterious force known as dark energy. Stars continue to form and die, galaxies evolve, and the cosmos marches on toward an unknown future.
