**2. How to Transform a Chloroplast in Three Steps**

Plastid transformation can be divided into three steps: first, foreign DNA is delivered to cells of an explant [41]. Second, the foreign DNA is inserted into the chloroplast genome through homologous recombination at a predetermined and precise location. Third, candidate transformants are repeatedly screened on selection medium until the wild-type genome is eliminated (a state known as homoplasmy) [9]. Positive explants are then regenerated into stable transgenic plants.
