Gazprom, an industrial and financial conglomerate created in 1992, is the key weapon in the Kremlin's geopolitical strategy. First producer of natural gas, Russia indeed holds a third of the world's total reserves. Responsible for producing, distributing and selling it, Gazprom is a company like no other, where gas market professionals work, but also ministers, deputies and advisers close to the Russian president. It was during the winter of 2005-2006 that Europe, which buys 30% of its gas from Russia, suddenly became aware of its vulnerability. Comment ? Overnight, Russia had just cut gas supplies to the pro-Western Ukraine of Viktor Lushchenko, who refused to pay tariffs multiplied by five. Since then, the continuous rise in oil prices, coupled with ever-increasing Chinese demand, has confirmed the key role that its hydrocarbons give to Russia.