Arrays of chlorophyll molecules harvest energy from sunlight and transfer it efficiently to the reaction center via ultrafast energy migration during photosynthesis. This lecture will present synthetic light-harvesting systems that mimic these energy transfer processes. Recent results on the delocalization of singlet excited states, triplet excited states and charge in porphyrin-based nanostructures will also be presented, including charge-transport measured through single molecules. A recurring question in these experiments is whether transport occurs by quantum coherent tunneling or incoherent multi-step hopping. The study of aromaticity and antiaromaticity in cyclic delocalized states will be discussed as a test for coherence.