Artwork of a section of human skin showing the relative degree of penetration of three types of laser beams used in medicine. The green argon laser at left penetrates the epidermis (the upper,purple skin layer) & is used to seal the dilated blood vessels that form a haemangioma. The tunable dye laser (orange, centre) does not penetrate the epidermis. At right the colourless carbon dioxide laser penetrates through to the dermis (buff coloured layer), which allows it to be used in the removal of unwanted tattoos. Dark spots (right) represent packets of tattoo pigment.