The total solar eclipse is finally here

The first glimpses of the first total solar eclipse to cross the United States from coast to coast in 99 years are now visible. What started as a tiny crescent of the moon's shadow has turned into a perfectly beautiful eclipse. It started in Oregon and is making a diagonal trek across the country, ending in South Carolina just after 4 p.m. ET.

During totality in Oregon, it looked like nighttime outside, with stars appearing in the sky and the temperature dropping.

NASA -- which is all about the eclipse today -- is having a bit of fun with it, tweeting a joke about the moon blocking the sun -- on social media.

"HA HA HA I've blocked the Sun! Make way for the Moon," said the official NASA Moon account, which blocked the NASA Sun's account.

Along with the moon and some sunspots, the International Space Station made a cameo in front of the sun. If you look very closely, you can see it.

If it hasn't yet reached your area, here's what you can do to be prepared:

-- Keep up with the forecast to make sure you won't be rained or clouded out.

-- Make sure you know everything about safely viewing the eclipse.

-- Any animals nearby? Keep an eye on their behavior.

-- Look on social media to see how all the various science experiments are going.

-- If you're stuck inside, follow along with virtual reality and 360 video on CNN.

-- Get your camera or phone ready!

-- Don't have glasses? Here's how to make them in less than 10 minutes.

-- Watch Bonnie Tyler sing "Total Eclipse of the Heart."

-- Read all the tweets and reactions or follow CNN's live blog.

-- Anything you don't see here? It's in our last-minute cheat sheet.

And don't forget to share your view with us.