Crowds in Texas witness the total solar eclipse turn the sky completely dark during the middle of the day.
The phenomenon was first seen in the Mexican resort town of Mazatlan.
At the point of totality, the Moon perfectly blocks the Sun. It lasts for about four minutes.
People are gathered across North American cities that lie in the path of the eclipse, as it continues its sweep north and east across 13 US states. It will finish in Canada.
The total eclipse will be watched by tens of millions as it continues for the next hour or so.
Nasa will be conducting experiments, flying planes and rockets to study the Sun's atmosphere.
To enjoy the phenomenon safely, never look at the Sun with the naked eye, even with sunglasses on - wear solar eclipse glasses.
