How the left-right body axis is established during development and how abnormal sidedness of asymmetric body structures i.e., laterality defects or situs inversus (seeNote 1 ), is induced during development have been questions of great interest in the history of science. A recent discovery of signaling molecules that are asymmetrically expressed before the establishment of morphological asymmetry in the chick embryo by Tabin and colleagues (1 ) has fueled the research of this area. Such investigations have been quickly expanded into mouse and rat embryos, the most commonly used mammalian experimental models (seeNote 2 ).
