Universe's structure

The universe is an immense, expanding space that contains all matter, energy, galaxies, stars, planets, and even empty regions known as voids. Galaxies are massive systems of stars held together by gravity, and they group into clusters and superclusters, forming a cosmic web of interconnected structures. Between these structures are vast voids with very few galaxies. On the largest scale, the universe appears uniform and isotropic, meaning it looks roughly the same in every direction, which suggests it originated from a hot, dense state known as the Big Bang and has been expanding ever since.