Visualize how the universe formed after the Big Bang, with this video from NOVA Wonders: What’s the Universe Made Of? Approximately 13.8 billion years ago, all the matter of the universe was compacted in a very small region of high density. In the first fraction of a second, there was an intense period of expansion known as cosmic inflation. The universe continued to expand and cool; after about 380,000 years, atoms formed and light was able to travel across space. Matter clumped together to form the structures of the universe and, as stars evolved and died, the chemical building blocks for planets and life were created. This resource is part of the NOVA Wonders Collection.