Molecular dynamics (MD) simulations of classical fluids have led to a revolution in our understanding of the equilibrium and non-equilibrium properties of fluids. In this book we have used MD method on fluids confined by membranes to study an equilibrium thermodynamic problem (solubility of gases in liquids) and a dynamic problem (permeation of gas in biomembranes). A simulation system with a selective permeable membrane in it to mimic a real experiment was developed. Computational studies were focused on gas solubility in equilibrated organic liquid systems and on the dynamics of gas...