Resolution of cosmological singularities in string theory

We show that a class of (3+1)-dimensional Friedmann-Robertson-Walker cosmologies can be embedded within a variety of solutions of string theory. In some realizations, the apparent singularities associated with the big bang or big crunch are resolved at nonsingular horizons of higher-dimensional quasi-black hole solutions (with compactified real time); in others, plausibly they are resolved at $D$-brane bound states having no conventional space-time interpretation.