One of the most deadly chemical weapons, "VX nerve agent", was used to kill Mr Kim Jong Nam, the estranged half-brother of North Korean leader Kim Jong Un, Malaysian police revealed on Friday (Feb 24).
The substance was identified in a preliminary report released by the Centre for Chemical Weapons Analysis of the Chemistry Department.
VX nerve agent is listed as a chemical weapon under Schedule 1 of the Chemical Weapons Convention Act 2005 and Chemical Weapons Convention (CWC) 1997.
Here are five things about this lethal weapon:
1. It is the most potent of all nerve agents
Developed in the United Kingdom in the early 1950s, VX is a nerve agent also known by its chemical name S-2 Diisoprophylaminoethyl methylphosphonothiolate.
Nerve agents work similarly to pesticides, but are far more potent - being the most toxic and rapidly acting of chemical warfare agents.
The lone recorded human fatality caused by VX is in Japan in 1994, when a Japanese doomsday cult, Aum Shinrikyo, used it to assassinate a former member.
VX may also have been used in the Iran-Iraq War in the 1980s.
VX boasts the dubious distinction of being classified as a weapon of mass destruction by the United Nations.
2. You might not even know you were hit by it
The best weapons are arguably those that cannot be detected by one or more of one's senses and VX fits the bill.
It is odourless and tasteless, so you might not even know you had been exposed to it.
However, if you have symptoms like blurred vision, chest tightness and nausea, you may have been affected by a low to moderate dose of VX.
Exposure to a large dose of the oily, amber-coloured liquid can result in convulsions, loss of consciousness, paralysis and respiratory failure, which could lead to death.
3. It takes effect very fast
If you have been hit with the vapour form of VX, symptoms will appear within a few seconds.
The liquid form can cause symptoms appearing within a few minutes to up to 18 hours.
VX works its toxic effects by disrupting an enzyme that acts as the body's "off switch" for glands and muscles.
The missing "off switch" means that the glands and muscles are constantly being stimulated, tiring them out and possibly making them unable to sustain breathing function.
As a protective measure, immediately leave the area where VX was released.
If you are outdoors, head to the highest ground possible because VX sinks to low-lying areas since it is heavier than air.
Those who have been exposed should remove their clothing, wash their entire body with soap and water, and get medical help as soon as possible.
4. It can spread easily and lasts a long time
Airborne VX can affect people through skin contact, eye contact or inhalation.
Your clothing also spreads the chemical once it has been in contact with VX vapour.
Drinking or getting contaminated water on your skin, and eating contaminated food also exposes you to the chemical.
VX breaks down slowly in the body, so it can build up in your body after repeated exposure.
It also takes a long time to evaporate - about as slowly as motor oil - so it can last for days on objects contaminated with it.
Very cold conditions extend its lifespan to months.
5. It is not the only chemical agent used in wars
Another nerve gas, Sarin, was most recently used in 2013 against rebels in the Syrian capital of Damascus.
Sarin is a liquid that is clear, colourless and tasteless, and can evaporate into a gas.
It has similar effects to VX and was also used in 1995 terrorist attack by doomsday cult Aum Shinrikyo in the Tokyo subway.
The attack killed 13 people and left more than 6,000 sick or injured.
Industrial chemical turned war weapon, phosgene was used so effectively in World War I that it was responsible for the majority of deaths.
Phosgene is a poisonous gas at room temperature and can spread rapidly.
It may cause delayed effects that are not apparent for up to 48 hours after exposure, such as difficulty breathing, low blood pressure and heart failure.
SOURCES: Reuters, The Guardian, The Japan Times, US Centres for Disease Control and Prevention