  We discuss the gauge theory mechanisms which are responsible for the causal
structure of the dual supergravity. For D-brane probes we show that the light
cone structure and Killing horizons of supergravity emerge dynamically. They
are associated with the appearance of new light degrees of freedom in the gauge
theory, which we explicitly identify. This provides a picture of physics at the
horizon of a black hole as seen by a D-brane probe.
