1. A system for hair transplantation, comprising: an interface adapted to receive an image data containing a follicular unit (FU); and an image processor comprising one or more modules for executing operations on the image data, the one or more modules including instructions for: determining an emergence angle of the FU; selecting or using pre-selected minimal approach angle of a tool used in transplantation of follicular units; comparing the emergence angle of the FU with the minimum approach angle of the tool; and determining the orientation of the tool based on a result of the comparison of the emergence angle of the FU with the minimum approach angle of the tool.