Porous media theories play an important role in many branches of engineering, including material science, the petroleum industry, chemical engineering, and soil mechanics, as well as biomechanics. This book offers a consistent treatment of the material-independent fundamental equations of the theory of porous media, formulates constitutive equations for frictional materials in the elastic and plastic range, and traces the historical development of porous media theory. Thus, for the first time, a unique treatment of fluid-saturated porous solids is presented. The corresponding theory is explained by its historical progression, and its current state is thoroughly described.