VX is a type of chemical weapon called a nerve agent. It is a very toxic chemical. Because it is so toxic, it cannot be used as anything other than a chemical weapon. The United Nations classifies VX as a weapon of mass destruction.
VX is the most toxic nerve agent ever created. The Council on Foreign Relations says: "A fraction of a drop of VX, absorbed through the skin, can fatally disrupt the nervous system."
The Chemical Weapons Convention of 1993, an international law, made it illegal for countries to use chemical weapons like VX. It also made it illegal to make or keep more than 100 grams of VX. It allows some scientists to make and use amounts under 100 grams only if they are trying to create an antidote, or doing medical research.