Orthodontists describe the current status of Twin Blocks, a techniques developed in 1977 to improve facial aesthetics in the correction of severe tooth malocclusion and now the most popular functional appliance worldwide. Recent developments incorporated into the third edition include pitfalls in appliance design and management, fixed Twin Blocks, fixed functional appliances, treating sleep apnea, breathe easy Twin Blocks, TransForce lingual appliances, and reverse Twin Blocks. Among other topics are diagnosis and treatment planning, combination therapy, magnetic Twin Blocks, and the flat Earth concept of facial growth. Annotation ©2015 Ringgold, Inc., Portland, OR (protoview.com)