On August 21, the sun will disappear for a short time.
For a swath of the country from Portland, Oregon, to Charleston, South Carolina, it will feel like someone just turned off the sun in the middle of the day.
Even if you live elsewhere in the US, a portion of the sun will partially disappear.
It is being called the "Great American Eclipse." And you can mark it on your calendar down to the millisecond.
It's been 99 years since a total solar eclipse crossed the country from the Pacific to the Atlantic. The total solar eclipse on June 8, 1918, crossed the States from Washington to Florida.
During the celestial event, the moon will pass in between the sun and the Earth, appearing to block the sun for almost an hour and a half.
Space enthusiasts are already starting to get excited for the eclipse, some counting down the days, while others are booking hotels for the big moment.
The Adler Planetarium is also preparing in advance with a new temporary exhibit called Chasing Eclipses.
The exhibit is opening its doors in about a week and will explore the history of the solar eclipse's past and what to expect this coming summer.
Inside the exhibit you can find yourself in the shadow of the moon, take a look at the artifacts scientists have used for years to study eclipses, and check out some of the tools used to watch them or build one yourself.
Why all the excitement this far in advance? It's been 210 years since Chicago has been this close to the path of totality for a solar eclipse, meaning a complete blackout. On August 21st, the moon will block 80 percent of the sun in Chicago.
One of the prime viewing spots for this eclipse is going to be in Carbondale Illinois about a five hour drive from Chicago. Southern Illinois University is planning a huge event that weekend and are expecting several thousand people to come.
NASA will even be broadcasting from the event, and experts predict the August eclipse may be the most viewed eclipse ever.
If you miss it, the next solar eclipse in the US happens in 2024, but it won't be this close to Chicago again until the year 2099.