Transit of Venus: What is it and who can see it?
The transit of Venus, where the planet Venus passes directly between the Earth and the Sun, will begin at 2204GMT/2304BST on Tuesday 5 June and will end at 0455GMT/0555BST.
As it happens, Venus appears as a small black dot moving across the surface of the Sun.
Here, science presenter Liz Bonnin explains how the transit works and why it is such a rare event - the next one will not happen until 2117. She also explains which parts of the world will be able to see the 2012 transit.