Jan Baptist van Helmont was a chemist, physiologist, and physician from the Spanish Netherlands. He worked during the years just after Paracelsus and the rise of iatrochemistry, and is sometimes considered to be "the founder of pneumatic chemistry". Van Helmont is remembered today largely for his ideas on spontaneous generation, his 5-year willow tree experiment, and his introduction of the word "gas" into the vocabulary of science.
His name is also found rendered as Jan-Baptiste van Helmont, Johannes Baptista van Helmont, Johann Baptista von Helmont, Joan Baptista van Helmont, and other minor variants switching between von and van.