Coldplay lead singer Chris Martin wrote "The Scientist" after listening to George Harrison's All Things Must Pass. In an interview with Rolling Stone, Martin revealed that while working on the band's second album, A Rush of Blood to the Head, he knew that the album was missing something. One night, during a stay in Liverpool, Martin found an old piano that was out of tune. He wanted to work on Harrison's song, "Isn't It a Pity", but he could not manage to do so. When the song came to Martin, he asked that the recorder be turned on. He concluded by saying that he came across this chord sequence and noted that the chord was "lovely". Martin recorded the vocals and piano takes in a studio in Liverpool.

In 2011, Willie Nelson covered the song for a Chipotle Mexican Grill-sponsored short film titled Back to the Start, highlighting the problems of concentrated animal feeding operations. It also appears as the final track on his 2012 album Heroes. 

Source: Wikipedia