The axion arises in the course of an elegant solution of the strong CP problem.
In addition, it is a very good candidate for dark matter and may explain the excessive cooling of stars in various stages of their evolution. Moreover, the saxion may play the role of the inflaton,
leading to a very predictive and distinctive cosmological history of the universe.
There are new, relatively small experiments around the globe, which are hunting the axion and complement the search for physics beyond the Standard Model at the Large Hadron Collider.