This work addresses the origin and evolution of new gene functions. Although interest in evolutionary novelties can be traced back to the time of Darwin, the appreciation and systematical experimental pursuit of the origin and evolution of new gene functions did not appear until the early 1990s. Sixteen chapters from pioneers and leading scientists in this emerging field provide overviews of how new genes with novel functions originated and evolved. Broad issues related to new gene evolution are analyzed, ranging from molecular mechanisms to population genetics to theoretical conjecture of the minimum building blocks for protein diversity. Both insightful reviews and original results of theoretical and experimental analyses are presented, which should be valuable for researchers and students in further pursuit of the field of new gene evolution.