There's an astronomical event happening on Monday called the transit of Mercury.
It sounds a bit Doctor Who, but the concept is actually simple: From our perspective, Mercury will travel in front of the sun.
The picture above shows a time lapse of the last time it happened, in 2006. That tiny dot going across the sun is Mercury.
Most places in the world (including Europe, Asia, Africa, North America, South America, the Pacific, the Atlantic, the Indian Ocean, the Arctic, and Antarctica) will be able to see at least some of the transit. In the UK, we'll be able to see the whole thing!
Mercury's first contact with the sun will be at 12:12pm BST (that's 11:12am UT for anyone in a different timezone). It'll reach its midpoint at 3:57pm and finally leave the sun's disc at 7:42pm.
Because Mercury is so small, you'll need a telescope (with a solar filter) to be able to see it. But luckily, astronomical societies across the UK will be hosting events for people to watch.
But if you're stuck in the office, or the sky clouds over, don't despair. You can also watch the transit online.
ESA will have a live stream of the event. Check here for a link on Monday.
The Slooh Community Observatory will also be live-streaming here.