The internal structure of extremal and near-extremal black holes in string theory involves a variety of ingredients — strings and branes — that lie beyond supergravity, yet it is often difficult to achieve quantitative control over these ingredients in a regime where the state being described approximates a black hole. The supertube is a brane bound state that has been proposed as a paradigm for how string theory resolves black hole horizon structure. This talk will describe how the worldsheet dynamics of strings can be solved exactly in a wide variety of supertube backgrounds, opening up the study of stringy effects in states near the black hole transition.