The knot contact homology is an algebraic invariant of knots in $R^3$. Its
topological definition was given by Ng. Later, it was confirmed by
Ekholm-Etnrye-Ng-Sullivan that this invariant agrees with the Legendrian
contact homology of the unit conormal bundle of knots, which is an
algebraic object defined by using pseudo-holomorphic curves. In this talk,
I will review some topological aspects of the knot contact homology. Then,
I will show its application via symplectic field theroy to a problem about
clean intersections (along knots) of Lagrangian submanifolds in the
cotangent bundle of $R^3$.