" They would have to do the research themselves. How large was a natural gas molecule, how large was an oil molecule, and how big before and after fracking would be the pore spaces—the tiny spaces or holes, invisible to the naked eye, in the rock? After investigating the matter with electron microscopes and a CT scan and thin slices of cores, they had the answer—an oil molecule was anywhere from slightly bigger than a gas molecule to seven times bigger. But, crucially, oil molecules of even that size could slide through the “throat” of the pore. "

― Daniel Yergin , The New Map: Energy, Climate, and the Clash of Nations