Its always interesting to study mechanism of tooth movement during orthodontic therapy. Deep understanding of orthodontic tooth movement helps to render best treatment strategies and prevent unwanted effects. After 100 years, there is a good understanding of the sequence of events at both tissue and cellular levels and now the current focus of research is at the molecular level. This textbook clearly demonstrates all the interactions between the cell and involvement of various cytokines, growth hormones, endocrine cells etc during OTM. All the cellular activities are described at molecular level happening during orthodontic tooth movement.