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.