Track Effects in Positronium Formation

We discuss some aspects important for interpretation of the Ps formation process in liquids and molecular media: (1) inhomogeneity of intratrack reactions and parameters of the e⁺ track, (2) final states of e⁺, its solvation in polar and nonpolar liquids, relation to e⁺ mobility, (3) quasi-neutrality of the e⁺ blob and its ambipolar outdiffusion, (4) appearance of the "in-blob" and "out-of-the-blob" positron fractions, and (5) electric field effect on Ps formation.