The powerhouse sister act is back with a new song a decade in the making.

On Friday (November 3), Aly & AJ released "I Know," the second song from their new EP, Ten Years. The track comes on the heels of the EP's first single, "Take Me."

"I Know" has a fun '80s vibe brimming with a pop synth sensibility, but it stems from a much more serious moment in the sisters' lives.

"This song was written a few days after we found out an acquaintance from our past had lost his battle with cancer," Aly & AJ share. "After seeing such an outcry of love and support from his close friends and family we decided to write something dedicated to friendship and the commitment we are all capable of giving when someone needs us most."

"I Know" is already an unabashed smash, having been streamed three million times on Spotify and soaring to the top of the US Viral 50 chart. Listen below:

Ten Years, out November 17, marks the duo's first collection of new music in a decade, excluding the song "Hothouse," which they put out under the name 78Violet. You can see that video below.

All the Records Dropping Fall 2017:

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