Several methods are being pursued for controlling gene expression spatially, temporally and in different degrees. One method is by using operon inducer/repressor system which provides temporal control of gene expression. To control gene expression spatially inkjet printers are under development for printing ligands on gel culture. Other popular method involves use of light to control gene expression in spatiotemporal fashion. Since light can also be controlled easily in space, time and degree, several methods of controlling gene expression at DNA and RNA level have been developed and are under study. For example, RNA interference can be controlled using light and also patterning of gene expression has been performed in cell monolayer and in zebrafish embryos using caged morpholino or peptide nucleic acid demonstrating the control of gene expression spatiotemporally. Recently light based control has been shown at DNA level using transgene based system or caged triplex forming oligos