One of the most signifi cant fi ndings revealed by analysis of genomes of multicellular organisms is the large number of genes for which no function is known or can be predicted (Alonso et al. 2003). Functional genomics is a relatively new technology that uses high throughput methods to analyze a large number of genes at a time. It studies the function of individual or groups of genes. Functional genomics allows researchers to gain an understanding of the control of genes during normal growth and development, and in response to environmental stresses. Researchers can further investigate the complex interactions that occur in genetic and cellular networks and ideally, the technology will allow the entire genetic make-up of an organism to be studied.