In 2005, Richard Schrock received the Nobel Prize in Chemistry, with Robert H. Grubbs and Yves Chauvin, for his work in the area of olefin metathesis, an organic synthesis technique. Schrock was the first to elucidate the structure and mechanism of so-called 'black box' olefin metathesis catalysts. Initial work at DuPont involved the synthesis of tantalum alkylidenes, alkylidenes being a crucial resting state in the catalytic cycle of olefin metathesis. His work at MIT has led to a detailed understanding of a group of molybdenum alkylidenes and alkylidynes which are active olefin and alkyne methathesis catalysts, respectively. Schrock has done much work to demonstrate that metallacyclobutanes are the key intermediate in olefin metathesis, with metallacyclobutadienes being the key intermediate in alkyne methathesis.