The discovery in 1988 of the giant magnetoresistive(GMR) effect is considered the beginning of the new, spin-based electronics. The physical basis for the observed effects is presented, and the initial successful applications of these phenomena and materials for information storage are reviewed. GMR read-head sensors have already created a multibillion dollar industry and magnetic random access memories using the tunneling magnetoresistive(TMR) effect will soon start another multibillion dollar industry. Spintronics is based on the up or down spin of the carriers rather than on electrons or holes as in traditional semiconductor electronics. This offers opportunities for a new generation of devices combining standard microelectronics. To successfully incorporate spins into existing semiconductor technology, one has to resolve technical issues such as efficient injection, transport, control and manipulation, and the detection of spin polarization as well as spin-polarized currents. The current state-of-the-art of spin-based devices, efforts in new materials fabrication, and optical spin coherent state manipulation are reviewed.