Orthodontic treatment without braces has been introduced more than half a century before clear aligners have been introduced in orthodontics. Clear aligners have been utilized to treat minor crowding for more than a decade. However, in the last few years, there has been increased interest and many publications came out in different prestigious peer reviewed journals about the possibility of using clear aligners to treat difficult orthodontic cases. Different companies that manufacture clear aligners for orthodontic tooth movement spent a huge time span and resources to optimize treatment results and to provide more controlled tooth movement. The research and development included, but not limited to design attachments that can provide optimum tooth control, develop new plastic material that can have shape memory in order to maximize its efficiency in tooth movement and developing protocols for different malocclusions. There is a huge global interest in using clear aligners in orthodontics, however it might take decades for traditional orthodontists to adopt clear aligners in orthodontic practice. This chapter will briefly review the available literature about the background of clear aligners and its future application in orthodontics.