Compared with the traditional crypto- graphy, visual cryptography (VC) decrypts secret images referring to the characteristics of human vision, rather than the cryptography knowledge or complex computations. Furthermore, seeing to the freeness of the secret key, the whole process of encryption as well as decryption for the visual cryptography meets a fast dealing course. As to the security concern, it is able to guarantee that no one can have access to any clues about the content of a secret image from individual cover images. Thus, owing to the studies on this area, the target of light-weighted cryptography is reached. Now the visual cryptography has been developed from the meaningless shadows to the meaningful ones. Seeing to the highly developed technique, some advanced VC techniques are introduced in this survey, respectively.