Starting with a CT scan of a person known only from a skull, Mr. Froesch digitally reconstructs the layers of muscle, skin and hair until he achieves the living appearance of the person.
These images show Mr. Froesch's reconstruction of the face of Simón Bolívar (1783-1830).
Fortunately, Bolívar is known from contemporary portraits, which helps a great deal.
This video shows some of the other faces he has reconstructed from skulls. (Video link) When it comes to prehistoric humans, reconstructions are more speculative, especially when it comes to soft morphology, such as ears, lips, and noses. Like a lot of other kinds of digital graphics, these images suggest a greater level of certainty than anthropologists really have.