The No One hitmaker quickly wrote the track after hearing about Aaliyah's passing in 2001.

"I was on a plane, and I think being on a plane and knowing she passed away after a plane crash, there was just this sentiment of being present in the moment and really nothing else mattering but those that you love," Keys says in a behind the scenes clip for her U.S. competition show The Voice. "I think that feeling was really present in my life at that time and really right in my face."

Writing the song was an easy process for the 36-year-old, but she admits she had difficulty composing it.

"I wrote it really quickly, but in order to produce it the way that you hear it, it took forever," she continues. "Nothing would come out right. Every version that I did, every arrangement that I did was just wrong. It was such a labor of love."

The song was released in 2003 on Alicia's second studio album The Diary of Alicia Keys and it remains one of her most cherished tracks to this day.

"It's definitely one of my favorite songs and I know a lot of people love that song...," she adds.