Discovering accurate relations between microstructure and elastic properties of porous/microcracked solids always was a challenging task in material science. In the book these relations are investigated on an example of sintered hydroxyapatite and Fontainebleau sandstone. It is shown that isolated pores of irregular shapes may be approximated, with good accuracy, by the spheroidal ones. Several commonly used approximate schemes are applied to predict effective Young's and shear moduli of a material with spheroidal pores. The microstructural information (average shapes of pores) required for adequate modeling of the isotropic elastic properties is identified; if this information is utilized, the usual effective media schemes provide satisfactory predictions of the effective elastic properties. An attempt was made to recover the information about evolution of microstructure from the experimentally measured elastic moduli. The book addresses researchers, graduate and postgraduate students, as well as engineers, in the fields of micromechanics of solids and materials science.