[3] In the late seventies, during America's withdrawal from Mainland Southeast Asia, Hmong people reported a "mysterious, lethal substance" called yellow rain.

In 1981, the United States government accused the Soviet Union of biological warfare, identifying yellow rain as trichothecene.

Later, in 1985, a study in Scientific American argued that yellow rain was merely feces released by apis dorsata, a type of honeybee in the region.

Despite an investigation between governments and scientists, as well as the United Nations, ensuing henceforth, a conclusion to the matter of yellow rain has never been institutionally declared.

[5] While in college, Vang learned about yellow rain, but it wasn't until a controversial Radiolab episode on the topic aired in September of 2012—which involved a provocative exchange against Hmong refugee Eng Yang and his niece, Kao Kalia Yang—that, in Vang's words, "yellow rain blew everything open in my life".