This article will introduce the reader to the emerging non-volatile memory (NVM) technologies, such as MRAM, PCRAM. NVM technologies combine the density of DRAM, the speed of SRAM, and the non-volatility of Flash memory, these technologies are very attractive to future generation universal memories. Emerging NVM cell characteristics are summarized in this article. The ideal characteristics for a memory device include fast write/read speed (≺ns), low operation voltage(≺1 V), low energy consumption (~fJ/b for write/read), long data retention time (≻10 years), long write/read cycling endurance (≻1017 cycles), and excellent scalability (≺10 nm). Nevertheless, it is almost impossible to satisfy all of these ideal characteristics in a single “universal” memory device. Several resistance-based emerging NVM technologies have been pursued toward achieving part of these ideal characteristics. The emerging NVM candidates include STT-MRAM ,PCRAM , RRAM , N-RAM, SONOS and FRAM.