Nearly 50 years have elapsed since the seminal heterosis conference was held at Iowa State College (Gowen, 1952). That conference undoubtedly grew out of the obvious importance of maize (Zea mays L.) hybrids in the agricultural economy of Iowa and the USA as well as the lack of understanding of the phenomenon of heterosis. Farmers in Iowa rapidly adopted maize hybrids. In just 15 years, Iowa went from 0 to 100% of the maize acreage being planted to hybrids. Gowen (1952) stated the following about hybrid maize "It seems likely that in no other period of like years has there been such an increase in food produced over so many acres of land. The return from hybrid corn has been phenomenal, but it is now evidently approaching an asymptotic value." If only Gowen could have looked ahead 50 years, because the best was yet to come (Fig. 4-1).