  An exotic approach to hadrons is discussed. It is based on the recently
developed open-closed string duality explicitly conjectured as the AdS/CFT
correspondence. Mesons as well as pentaquarks are studied in this approach.
Spins are introduced as distribution functions over the string, and a second
quantization method of string theory is examined and used to estimate the mass
and decay width of various hadrons. This approach provides a way to understand
the structure of flavor by a configuration of probe branes.
