Our universe began with a hot big bang 13.7 billion years ago and has expanded and cooled ever since. It has evolved from a formless soup of elementary particles into the richly structured cosmos of today.
The first microsecond was the formative period when matter came to dominate over
antimatter, the seeds for galaxies and other structures were planted, and dark matter (the unidentified material that holds those structures together) was created.
The future of the universe lies in the hands of dark energy, an unknown form of energy that caused cosmic expansion to begin accelerating a few billion years ago.