The state of knowledge in the field of structure-function relationships in the chlorophyll (Chl) a/b containing light-harvesting antenna complex II (LHC II) of higher plants as a result of 25 years of interdisciplinary research is summarized. The review will start with first attempts to employ non-linear optical effects to gain insight into structure-function relationships in light-harvesting antenna complexes. Special emphasis will be given to relating the recent advances in structure elucidation of LHC II to its (non-linear) spectroscopic properties. The concept of Chl-forms (i.e. spectral substructures in the antenna absorption bands) is re-evaluated in terms of both their origin and functional implications. Related to this, consequences for energy transfer mechanisms (coherent vs. non-coherent) are discussed. Principles and contents of information of the applied non-linear laserspectroscopic techniques will be described, including Non-Linear Polarization Spectroscopy in the Frequency Domain and Non-Linear Absorption Spectroscopy.