Synthetic biology has eluded precise definition since its early days at the turn of the 21st century. At its heart are the goal of engineering biology to control living systems and the practice of assembling a synthetic system from component parts. However, the boundaries of synthetic biology as a discipline are hazy. It is difficult to gauge its success until one examines how it manifests itself in other fields. Although not commonly branded as such, the fields of protein engineering, optogenetics, and genome editing all participate in synthetic biology (they are part of synthetic biology and synthetic biology is part of them).