The 3-D printing technology has made many people excited about new applications. Currently used printers have many limitations. Up until recently, most 3-D printers can only use plastic. A group of researchers have started to develop new 3-D printer inks. The team prints intricate objects chooses using materials based upon their mechanical binding, electrical conductivity, or optical traits. As a result new inks will enable a wider variety of functions, including artificial human organ creation, and understanding complex human body.