Tetrathiafulvalene is a fascinating system: it is quite rare to find a synthetic molecule endowed with such a simple architecture that is capable of concentrating intense interest from various communities of chemists. This success results from the conjunction of intrinsic structural and electronic properties: structurally, this sulfur-rich bicyclic compound is essentially planar (at least in the radical cation state) and therefore presents, as with most of its substituted derivatives, a good propensity to stack in the solid state. This parameter is favorable for efficient charge delocalization in the solid-state and it is this feature that gave birth to the first conducting and superconducting organic salts. This non-aromatic 14 π-electron system is readily oxidized through a reversible process to the corresponding aromatic cation radical and dication species. This excellent π-donating ability, coupled to the high stability of both oxidized species, has contributed to the establishment of this unit as a key contemporary building block for the construction of redoxactive molecular and supramolecular systems.