The LIM homeobox gene Lhx2 has been studied and found to be necessary for the normal development of the eye, cerebral cortex, and pituitary glands. In addition, it has been investigated for its role in diseases of the cerebral cortex, including schizencephaly, septo-optic dysplasia, and Joubert syndrome. Due to the importance of the Lhx2 gene, researchers have developed knockout mice without the Lhx2 gene. However, drawbacks to conventional “fixed” knockout mice of the Lhx2 gene include embryonic lethality and the inability to perform mosaic analysis of Lhx2 activation. Newer knockout models that address these drawbacks will allow researchers to enhance their studies of the Lhx2 gene. Researchers at the University of California, Irvine have developed a new Lhx2 conditional knockout mouse. This mouse line is unique in that the place and time of the inactivation of the Lhx2 gene can controlled. Also, this mouse line allows researchers to perform mosaic analyses and does not result in embryonic lethality.