Abstract
Understanding the neural mechanisms of memory has been one of the key questions in biology. Long-term memory, specifically, allows one to travel mentally without constraints of time and space. A long-term memory must have gone through a series of temporal processes: encoding, consolidation, storage, and retrieval. Decades of studies have revealed cellular and molecular mechanisms underlying each process. In this article, we first review the emerging concept of memory engrams and technologies of engram labeling, as these methods provide a new avenue to study the molecular mechanisms for memory. Then, we focus on DNA methylation and its role in long-term memory. Finally, we discuss some key remaining questions in this field and their implications in memory-related disease.