  Resonating Valence Bond states are quantum spin liquids, having low energy
spin-half (spinon) or spin-1 excitations. Although spins are `disordered', they
posses subtle topological orders and some times chiral orders. RVB states are
easily appreciated and seem natural in the quantum fluctuation dominated 1D
world. In 2 and 3D, competing orders such as antiferromagnetism, charge order
or even superconductivity often hide an underlying robust quantum spin liquid
state. Introduction of additional spin interactions or doping of delocalized
charges, or finite temperatures, could frustrate the long range magnetic order
and reveal a robust RVB state. To this extent they are natural in 2D and above.
We present a brief history of insulating RVB states. Then we summarise our own
recent theory of RVB states for 2 and 3D systems, including some newly
synthesised ones: i) boron doped diamond, ii) \nxcob, iii) quasi 2D organic
conductors and iv) a 2D graphene sheet.
