摘要: Spectroscopy usually employs one frequency axis along which the signal intensity is plotted. In high resolution NMR spectroscopy in liquids a wealth of overlapping lines different nuclear species commonly observed. The same statement applies to solid state especially if techniques are applied as described this monograph. reader should be aware, that so far only simple highly resolved spectra have been discussed order present examples. practice, however, with possibly near neighbour couplings do often overlap powder samples. A technique therefore desirable, second representing interaction spins than first one. would disentangled and correlations could visualized. Such was proposed for by Jeener [1] at summer school Jugoslavia has further developed Ernst coworkers [2–4] Freeman co-workers [5, 6]. Waugh [7–10], Stoll, Vega Vaughan [11] Alia Lippmaa [12] designed 2D-experiments specifically tailored applications. Since then numerous variations these basic experiments proposed. Some we will deal Sect. 5.4. Space does not permit complete review 2D-spectroscopy. We restrict ourselves principles (Sect. 5.1) some applications NMR.