2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/98882This is an extended version of the talk given by the author at the NATO Advanced Study Institute "Supersymmetry and Trace Formulae" (Isaac Newton Institute, Cambridge, UK, 8-19 Septemebr 1997). Contains the following sections: 1. Eigenfunction correlations in the weak localization regime. 2. Strong correlations of eigenfunctions and level repulsion at the Anderson localization transition. 3. Fluctuations in the addition spectra of quantum dots.16 pages LATEX, uses plenum.sty style file. To be published in the Proceedings of the NATO ASI "Supersymmetry and Trace Formulae". An error in a numerical coefficient on page 14 correctedDisordered Systems and Neural NetworksChaotic DynamicsMesoscale and Nanoscale Physicstext