Conformational dynamics and fluctuations are essential for molecules to react and function in condensed phase. As molecular understanding of these motions are difficult to reach via experiments, our lab use computer simulations and theoretical analyses to study chemical reactions and conformational transitions of molecules in solution. The goal is to elucidate the molecular mechanisms that lead to functions of biomolecules and macromolecules. We also develop theoretical approaches to reveal the hierarchy of events that occur in condensed phase.