  We briefly review the present status of string theory from the viewpoint of
its implications on the short-distance space-time structure and black hole
physics. Special emphases are given on two closely related issues in recent
developments towards nonperturbative string theory, namely, the role of the
space-time uncertainty relation as a qualitative but universal characterization
of the short-distance structure of string theory and the microscopic
formulation of black-hole entropies. We will also suggest that the space-time
uncertainty relation can be an underlying principle for the holographic
property of M theory, by showing that the space-time uncertainty relation
naturally explains the UV/IR relation used in a recent derivation of the
holographic bound for D3 brane by Susskind and Witten.
