6th International Symposium of JSPS Core-to-Core Program on “Molecular Recognition Mechanism between Flexible Molecules” was held on October 16-20 at Technical University Berlin, Germany. Prof. Matsumoto had an opportunity of the oral presentation “Hydration switching on the intermolecular orientation of pyrrole dimer cations probed by IR photodissociation spectroscopy”. In addition, Mr. Yuki Hayano (M1) presented his poster “Hydrogen bonding structures of propargyl alcohol clusters probed by IR cavity ringdown spectroscopy”.