Classification of admixtures influence of admixtures on nucleation - homogeneous nucleation heterogeneous nucleation secondary nucleation influence of admixtures on crystal growth - the role of the solid surface, the role of the interphase solid - liquid influence of admixtures on crystal shape influence of solvents distribution of admixtures - solid solutions, isomorphous inclusion, anomalous mixed crystals, adsorption inclusion, mechanisms of internal adsorption, mechanical inclusions, materials balance for crystallization in presence of impurities, cascade purification.