Microelectronics is based on the semiconductor components such as transistors and diodes, and electronic circuits for the processing and manipulation of electrical data. Such semiconductor components and electronic circuits are based on the transport, manipulation, and storage of charge. Over the past five decades, there has been tremendous reduction of the size of the transistor to improve performance of the devices. It is expected that this trend, so called “Moore’s law”, might approach a physical limitation, and perhaps, a technology more than scaling down the device size is required to continue the improvement of electronic devices. Given this, it is not surprising that alternative types of electronics are being developed. One such approach is spintronics, which represents an emerging field of electronics based on the spin of electron. Spintronics has unique fields of applications such as magnetic data storages and memories. Ferromagnets are used in those systems for long-term data storage and archiving. Here, the data are written into a ferromagnetic thin layer in the form of tiny magnetic domains with a given magnetization orientation, and spin-polarized current is used to switch magnetic domains and to excite magnetization precession by spin-transfer torque (STT). We present a brief review and outlook on the recent development of magnetoresistive random access memory (MRAM) and its applications.