Inspired by the now famous photo-shoot commissioned by "Life" magazine in 1955, LIFE reveals the unlikely friendship between unproven photographer Dennis Stock and a little-known actor on the cusp of stardom called James Dean. At the time Stock was 26, old before his time and tied down to family life, but anxious to prove himself as an artist. Into his buttoned-down world came rising star James Dean, a free spirit who would change popular culture from suits to jeans and from matinee idols to rebellious teenage heartthrobs. James Dean at 23 had mixed feelings about his impending stardom – the young actor was a frequent no-show at publicity events, famously infuriating studio boss Jack Warner – yet agreed to invite Stock into to his life to share vulnerable and honest family moments. The LIFE assignment, which would ultimately provide the world with some of the most lasting and iconic images of the age, took the pair on a road trip around the US and created a friendship that would change Stock’s life forever.