We knew when we met Gitanjali Rao that she was going places.

And this week, she went all the way from Lone Tree, Colo. to New York City for her late-night TV debut.

Gitanjali got Next's attention last year. She was named "America's Top Young Scientist" in 2017 - and we, of course, had to name her one of the Smartest Kids in Colorado.

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The now-12-year-old had invented a way to detect lead in drinking water that's faster cheaper than current methods. Her device - called Tethys for the Greek goddess of fres h water - connects to a smartphone app that gives you test results within seconds.

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Screenshot: The Tonight Show

Thursday, Gitanjali visited The Tonight Show and gave host Jimmy Fallon a demonstration, while also schooling him on all the science behind it.

She schooled us, too, when we visited her earlier this year. We caught up with Gitanjali while she worked with some scientists at Denver Water.

Gitanjali told Fallon that she'll be profiled in an upcoming documentary produced by Google.

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Screenshot: The Tonight Show

No word yet if Fallon will be included in the documentary for his own invention, which he showed off to Gitanjali on the show: thumb-bells - a workout for your thumbs in this modern world.

See it for yourself in the clip (Click here if it doesn't appear):

And as always, Next is looking for more of the Smartest Kids in Colorado. If you know one of those, email next@9news.com.