We discuss the structures of exotic candidates and why it is interesting to measure them in heavy ion collisions. take X (3872) T cc illustrate our point.

A brief review of some topics in hadron production from heavy ion collisions is given. They include charged pion ratio as a probe nuclear symmetry energy, in-medium effects on production, en- hanced Λ c / D 0 ratio, local polarization, and X (3872) production.