From Wikipedia:

[font=Times New Roman]Subsurface scattering is important in 3D computer graphics, being necessary for the realistic rendering of materials such as marble, skin, and milk.... This technique was pioneered in rendering faces in The Matrix Reloaded [4], but has recently fallen into the realm of real-time techniques.[/font]

link : http://en.wikipedia.org/wiki/Subsurface_scattering