This celestial event won't happen again for 105 years. It began at 3:06 p.m. PT and will last until 8:02 p.m.
It will take hours to move across the sun before it will be at its most spectacular at sunset. The sun will go down before the transit is complete.
This event happens twice every 120 years. Tuesday it will be visible across all of North America for the first time since the 19th century. It won't happen again until 2117. The event has only happened six times since the telescope was invented.
"This is claimed to be the longest-interval astronomical event that you could predict well into the future," said David Nakamoto, Los Angeles Astronomical Society.
People gathered at the Griffith Park Observatory to watch the transit of Venus Tuesday afternoon.
If you take it in, be warned never to look at the sun without the appropriate eyewear, like welding glasses or specialized shades you can buy at the planetarium.
Or you can look through a telescope, like the ones volunteers are bringing to the observatory Tuesday to share in the celestial experience with other earthlings.