The thick, gooey substance that has caused chemical-like burns in a slew of vaping-related illnesses across the country was discovered at a lab in upstate New York.

Last week, the Centers for Disease Control and Prevention (CDC) announced a breakthrough and said scientists had discovered a potential suspect in Vitamin E acetate.

The 'chemical of concern' clings to the lungs when it's inhaled and causes burns that have been likened to those suffered by soldiers attacked with mustard gas during World War I.

Since March, 2,172 Americans have been sickened and at least 42 in 24 states and the nation's capital have died from illnesses linked to e-cigarettes.

Good Morning America went inside the Medical Marijuana Laboratory of Organic and Analytical Chemistry at the Wadsworth Center in Albany, New York, to learn how scientists found the 'key culprit'.