Geological perspective and discussion of shale reservoired hydrocarbons (shale gas and shale oil) and the emotive process used to produce them, hydraulic fracturing or fracking in colloquial parlance, is timely, in view of the current debate on the potential for exploitation of shales in the UK. Fracking is a long-standing oil industry process which has recently allowed unconventional hydrocarbons to dominate much of the world oil industry. This is particularly so in the USA where their development has dramatically overturned the decline in domestic production, with the current attainment of near self-sufficiency in both oil and gas production. Exploration for, and production of, shale-reservoired hydrocarbons requires a very different approach and mind-set from that required for conventional oil and gas resources, as well as raising widespread concerns around environmental aspects of fracking. The aim of this paper is to discuss the geology of shale resources and the techniques developed for their exploration and exploitation and place the environmental issues in their geological, not socio-economic context.