Porphyrins are a class of brightly coloured compounds that occur widely in Nature, for example in chlorophyll, haemoglobin and cytochromes. The electronic properties of these molecules make them ideal for transporting energy from sunlight in photosynthesis. They can also be used to construct molecular wires that conduct electricity, and to make single-molecule transistors – the smallest possible electronic devices. Template-directed synthesis can be used to build molecular wire rings, as well as linear wires. In this talk, I will explain how we build porphyrin-based molecular wires and how we test their electronic properties