The Heineken company was founded in 1864 when the 22-year-old Gerard Adriaan Heineken bought a brewery known as De Hooiberg (the haystack) in Amsterdam. In 1869 Heineken switched to the use of bottom-fermenting yeast. In 1873 the brewery's name changed to Heineken's Bierbrouwerij Maatschappij (HBM), and opened a second brewery in Rotterdam in 1874. In 1886 Dr. H. Elion, a pupil of the French chemist Louis Pasteur, developed the "Heineken A-yeast" in the Heineken laboratory. This yeast is still the key ingredient of Heineken beer.