The universe is the vast expanse that contains all of space, time, matter, and energy. It includes everything from the smallest particles to the largest galaxies. Scientists believe the universe began with the Big Bang around 13.8 billion years ago, leading to its continuous expansion. Within the universe, there are billions of galaxies, each containing millions or even billions of stars. Our home galaxy is called the Milky Way, which is just one of many in the universe. The study of the universe is known as cosmology, and it helps us understand the fundamental laws of nature and our place in the cosmos.