To create an X-ray image, the artist begins by painting a silhouette of the figure, often in white, and then adding the internal details in red or yellow. For red, yellow, and white paints, the artist uses natural ocher pigments mined from mineral deposits, while black is drived from charcoal. Early X-ray images depict the backbone, ribs, and internal organs of humans and animals. Later examples also include features such as muscle masses, body fat, optic nerves, and breast milk in women. Some works created after European contact even show rifles with bullets visible inside them.