A seed, but is typically referred to as a grain. When cooked, quinoa expands and becomes soft and somewhat fluffy.

The Andes in South America.

Europeans attempted unsuccessfully to establish quinoa to Europe in the 1550s. It was not until the late 20th century that quinoa cultivation grew more widespread. 

The ancient Incas considered quinoa to be a sacred food. 

“A Brief History of Quinoa” by GoGoQuinoa https://www.gogoquinoa.com/a-brief-history-of quinoa 

New Oxford Book of Food Plants by John Vaughan et al. (2009)