In a candid moment of true backstage access, Paul McCartney and John Lennon warm up on their guitars in anticipation of their show at Olympia Stadium in Detroit, Michigan, on August 13, 1966. The two-show stop in Detroit drew a combined audience of 30,800 rabid Beatles fans and had an impressive set list: Rock and Roll Music, She’s a Woman, If I Needed Someone, Baby’s In Black, Day Tripper, I Feel Fine, Yesterday, I Wanna Be Your Man, Nowhere Man, Paperback Writer and Long Tall Sally. In this photograph, the creative energy between Lennon and McCartney is palpable. The legendary duo collaborated on some of the biggest records the world has ever seen, and did it all with a healthy amount of friendly competition. A writer for The Atlantic summed up their partnership best: “John was the badass older brother Paul never had. Paul was a charming sidekick who could do something rare: keep up with John.” The pair are notorious for their own version of call-and-answer: John’s Strawberry Fields Forever was answered by Paul’s Penny Lane; John’s Revolution 1 by Paul’s Blackbird. And so, one of the greatest songwriting duos of all time was created – in competition and in brotherhood – and captured beautifully here.