  We review the recent results of heavy meson diffusion in thermal hadronic
matter. The interactions of D and B-bar mesons with other hadrons (light mesons
and baryons) are extracted from effective field theories based on chiral and
heavy-quark symmetries. When these guiding principles are combined with exact
unitarity, physical values of the cross sections are obtained. These cross
sections (which contain resonant contributions) are used to calculate the drag
and diffusion coefficients of heavy mesons immersed in a thermal and dense
medium. The transport coefficients are computed using a Fokker-Planck reduction
of the Boltzmann equation.
