Were you aware that the toner cartridges we use today grew out of a process called "xerography"? The Greek words for "dry" and "writing" named the process used by the very first commercial copy machine in 1949, and this process of transfering dry ink (or toner) to a piece of paper is the basis of how laser printers work today!
Today, toner is composed of carbon powder and polymer or plastic resin that bonds to paper when passed through a printer's fuser - basically, they melt right onto, and into the sheet! This is why, unlike ink jet printer pieces, you don't having any "bleeding" of the finished piece, even if it gets wet after printing. Cool!