Genomics has changed the pace by which genes are analyzed. Rather than looking at genes one by one, gene expression today is studied at the genome level. Unfortunately, the data we get from microarray analysis do not give us any clues about the function of these genes. Functional analyses are still refractory to large-scale, high-throughput studies, particularly in vertebrates. With the development of in ovo RNAi as a tool for specific gene silencing, the chicken embryo has become an efficient in vivo system to study gene function during development. A major advantage of in ovo RNAi is the fact that the knowledge of a cDNA fragment of the gene of interest is sufficient to get loss-of-function phenotypes. Thus, this new approach is a valuable tool for functional genomics.