In string theory, D-branes are a class of extended objects upon which open strings can end with Dirichlet boundary conditions, after which they're named. D-branes were discovered by Dai, Leigh and Polchinski, and independently by Horava in 1989. In 1995, Polchinski identified D-branes with black p-brane solutions of supergravity, a discovery that triggered the Second Superstring Revolution and led to both holographic and M-theory dualities. D-branes are typically classified by their dimension, w… (More on D-branes)