Genesis of the concept: intermolecular ferromagnetic spin exchange; structural determinants of the chemical and magnetic properties of non-kekule molecules; antiaromatic triplet ground state molecules - building blocks for organic magnets. Theory of exchange in organic systems: resonating valence bond theory and magnetic properties; qualitative and quantitative predictions and measurements of singlet-triplet splittings in non-Kekule hydrocarbon diradicals and heteroatom derivatives. Exchange in small organic open-shell systems: conformational exchange modulation in trimethylenemethane-type biradicals; use of dinitrenes as models for intramolecular exchange; radical ion building blocks for organic magnetic materials - computational and experimental approaches. Exchange in polymeric organic systems: design and experimental investigation of high-spin organic systems; synthesis and properties of organic conjugated polyradicals; pendant and conjugated organic polyradicals. Theory of organic magnetism in condensed phases: band theory of exchange effects in organic open shell systems; orbital interactions determining the exchange effects in organic molecular crystals; molecular orbital theoretical elucidation of spin alignments in organic magnetic crystals. Magnetism in organic condensed phases: exchange effects in three dimensions - real materials bulk magnetic properties of organic verdazyl radical crystals; neutron diffraction studies of spin densities in magnetic molecular materials; heat capacity studies of organic radical crystals. Summation: an integrated approach to organic-based molecular magnetic materials.