INTRODUCTIONrnCleft palate is a common craniofacial malformation in humans, affecting approximately one in every 700 live births worldwide. During mammalian palatogenesis, the secondary palatal shelf (PS) undergoes dramatic morphological changes to elevate from the vertical to horizontal direction and finally separate the oral and nasal cavities. Because of the rapid process, the exact molecular mechanism still remains elusive.1-5 Several hypoth-eses about the morphological changes have been considered for decades. Walker and Fraser proposed that the PS rapidly remodeled itself by bulging a new protrusion on the lingual wall and regression at the original tip, and described that the PS reorientation proceeded in a wave-liking manner from posterior to anterior.1,4,6 Coleman found that the anterior part of the PS was elevated by a swinging“flip-up”process along the AP (anterior-posterior) axis, while the posterior and middle parts were reoriented through an oozing“flow”remodeling mechan-ism.1,7 Although both these authors believed dramatic mor-phological remodeling occurred during elevation in the posterior palate, little was mentioned about the decisive factor for the distinct elevation pattern along the AP axis.1,4,8 Several investigators hypothesized that the intrinsic bulging or swelling force, generated by the absorption of water by hyaluronan and glycosaminoglycan, expanded the extracellular matrix (ECM) to remodel the PS and accomplish elevation.1,3,8-10 For the above reasons, and the fact that aglossia could also be accompanied by the normal palatogenesis,11-12 some research-ers considered that the tongue was not important in assisting palatal elevation.5 However, some studies suggested that the lack of fetal tongue or mouth movement could also result in adelay in palatal elevation,13-14 implying the positive role of tongue in palatal elevation. Irrespective of the hypothesis, the tongue plays an important role in palatal elevation due to its key location in the oral and nasal cavities. However, because of the rapid process, it is difficult to capture the dramatic morphological changes of PSs as they conflicted with the tongue.