terpyridines with ruthenium, silver or other metal ions is of great utility in the construction of complex architectures of many individual molecules. The complexation of porphyrins or phthalocyanines around metal ions gives access to catalytic, photochemical and electrochemical properties in addition to the complexation itself. These units are used a great deal by nature. Macrocycles Macrocycles are very useful in supramolecular chemistry, as they provide whole cavities that can completely surround guest molecules and may be chemically modified to fine-tune their properties. Cyclodextrins, calixarenes, cucurbiturils and crown ethers are readily synthesized in large quantities, and are therefore convenient for use in supramolecular systems. More complex cyclophanes, and cryptands can be synthesised to provide more tailored recognition properties. Supramolecular metallocycles are macrocyclic aggregates with metal ions in the ring, often formed from angular and linear modules. Common metallocycle shapes in these types of applications include triangles, squares, and pentagons, each bearing functional groups that connect the pieces via "self-assembly." Metallacrowns are metallomacrocycles generated via a similar self-assembly approach from fused chelate-rings. Structural units Many supramolecular systems require their components to have suitable spacing and conformations relative to each other, and therefore easily employed structural units are required. Commonly used spacers and connecting groups include polyether chains, biphenyls and triphenyls, and simple alkyl chains. The chemistry for creating and connecting these units is very well understood. nanoparticles, nanorods, fullerenes and dendrimers offer nanometer-sized structure and encapsulation units. Surfaces can be used as scaffolds for the construction of complex systems and also for interfacing electrochemical systems with electrodes. Regular surfaces can be used for the construction of self-assembled monolayers and multilayers. The understanding of intermolecular interactions in solids has undergone a major renaissance via inputs from different experimental and computational methods in the last decade. This includes high-pressure studies in solids and "in situ" crystallization of compounds which are liquids at room temperature along with the utilization of electron density analysis, crystal structure prediction and DFT calculations in solid state to enable a quantitative understanding of the nature, energetics and topological properties associated with such interactions in crystals. Photo-chemically and electro-chemically active units Porphyrins, and phthalocyanines have highly tunable photochemical and electrochemical activity as well as the potential to form complexes. Photochromic and photoisomerizable groups can change their shapes and properties, including binding properties, upon exposure to light. Tetrathiafulvalene (TTF) and quinones have multiple stable oxidation states, and therefore can be used in