  By studying string loop corrections to superpotential of type II strings
compactified on Calabi-Yau threefolds we find a quantum stringy test and a
confirmation of a recent proposal of Strominger on the fate of the conifold
singularity. We also propose a connection between the spectrum of Bogomolnyi
saturated solitons and one-loop string partition function of $N=2$ topological
strings.
