A solar eclipse is sweeping across the US.
The Canadian Space Agency described the initial glimpses of the first total solar eclipse to sweep across the US, from Oregon to South Carolina, in 99 years as "Beautiful!" as Americans across watched in wonder through telescopes, cameras and protective glasses.
The watched as the moon blots out the sun and turns daylight into twilight.
Among the big names who had been excited by the spectacle were rock star Bruce Springsteen and Ivanka Trump, daughter of the US President Donald Trump, who tweeted safety advice warning watchers to remember to wear their glasses.
Totality - when the sun is completely obscured by the moon - lasts for around two minutes in each location along the narrow corridor stretching across the US. Southern-most Illinois will have the longest period of darkness at two minutes and 44 seconds.
It is expected to be the most-observed and most-photographed eclipse in history.
Gloomy skies means that Britons may be less lucky in seeing a a partial solar eclipse on Monday evening, forecasters have warned.
Just before sunset, the moon will appear to take a "bite" out of the sun in a phenomenon lasting roughly 40 minutes.
The mid-point will occur at different times around the UK, but overcast weather is likely to obscure the spectacle for most, the Met Office said.
The movement of the moon between the Earth and sun will produce a much more dramatic event in the US, where a total eclipse will turn day to night for two minutes.
On British shores, only south-west England and South Wales are expected to have any chance of witnessing the moment through a break in the cloud.
Met Office forecaster Martin Bowles said: "It doesn't look very promising.
"It is only going to be about 4% of the sun which will be blotted out, so even if it is perfect weather conditions, you won't see a lot.
"From a meteorological point of view, it is not looking very good because of the cloud. Most people won't be able to see a thing.
"There will be some breaks in the cloud in the south-west of the country - South Wales and south-west England - there will be enough breaks that people who are looking specifically might be able to see a little chip out of the corner of the sun.
"Anywhere in the east, including London, won't see anything because it will just be clouded over; also Scotland and Northern Ireland."
Due to the partial eclipse occurring near sunset, there is unlikely to be an observable reduction in light, he added.
For observers in Edinburgh, the peak of the eclipse is due to be at 7.58pm and for those in Cardiff at 8.05pm.
Up to five solar eclipses occur each year, but each one is visible only within a limited band across the Earth's surface where the moon's shadow happens to fall.
The Royal Astronomical Society warned anyone hoping to catch the phenomenon not to look directly at the sun.