Maxillary transverse deficiency is the primary cause of maxillomandibular transverse discrepancy, though in some cases, the issue may also arise from constriction in the posterior dentoalveolar region of the mandible. For growing patients with maxillary deficiency, maxillary expansion is the preferred treatment, with Rapid Palatal Expansion (RPE) proving effective for orthopedic expansion in children. However, RPE has limited skeletal effects in adults, particularly those with fully matured sutures. For such skeletally mature patients, Surgically Assisted Rapid Palatal Expansion (SARPE) is often the treatment of choice. In recent years, Miniscrew Assisted Rapid Palatal Expansion (MARPE) has emerged as an effective non-surgical alternative, particularly for young adults. This lecture will review contemporary methods for maxillary expansion in skeletally mature individuals, highlighting both surgical and non-surgical techniques, and addressing strategies for managing mandibular transverse deficiencies without surgery.