How was the Universe made?
Most astronomers think that the Universe was formed during an event called the Big Bang - a giant explosion which occurred between 10 and 20 billion years ago (see our "How Old is the Universe" page for a longer discussion of the age of the Universe...)
During the Big Bang, all of the space, time, matter, and energy in the Universe was created. This giant explosion hurled matter in all directions and caused space itself to expand. As the Universe cooled, the material in it combined to form galaxies, stars, and planets.
The size, shape, expansion rate and even what is inside the Universe comprises a large portion of ongoing modern astronomy research. To get started on exploring some of these potentially mind-boggling concepts, explore the NASA Astrophysics Science website.