Transverse expansion of the maxilla has been used by orthodontists for many years to correct maxillary arch discrepancy. Rapid mechanical maxillary expansion procedures as presently employed, utilize large loads designed to produce a maximal skeletal effect,but most of the case it is unstable. Correction of transverse discrepancy usually requires combination of both orthopaedic and orthodontic effect in order to correct crossbite. Tandem–loop nickel titanium NiTi, temperature–activated palatal expander with the ability to produce light, continuous pressure on the midpalatal suture and it helps in achieve both skeletal and dental effect on maxillary arch.