They had been fighting crime separately for years, but it wasn't until the historic Superman #76 in 1952 that Superman, the Man of Steel, finally teamed up with the Caped Crusader himself--Batman.
That story proved so popular that the team quickly became the main feature in World's Finest Comics--and thus the greatest partnership in comics was born.
Their adventures together would feature heroes and villains such as Robin, Batwoman, Lex Luthor, Bat-Mite, Mr. Mxyzptlk and more alien threats than might seem possible.
Batman & Superman in World's Finest: The Silver Age Vol. 2 collects their super-team-ups from World's Finest Comics #95-116.