Insight into the neurobiological mechanisms that underlie the processing of remote fear memories is crucial for our fundamental understanding of how the brain stores and retrieves information. Recent studies revealed that engram cells serve as the biological substrate of memories in the brain. It is hypothesized that synaptic connections of engram-cell networks, in cortical brain areas, lay the foundation of our brain’s capability to process distant fear memories. However, little is known about how engram-cell networks in the cortex adapt over time to store and maintain information regarding fearful experiences from the remote past. In my postdoctoral research, I investigate whether engram-cell networks are strengthened over time in the retrosplenial cortex to process remote fear memories. To examine these network-wide changes of fear-related engram cells, I will use newly developed optical approaches which enable me to precisely map large-scale synaptic networks with single-cell resolution. In addition, I will longitudinally follow the reorganization of engram cell networks in vivo to gain unique information regarding the circuit dynamics. Together, this set of experiments will gain an unique insight into the dynamics of functional connections that guide remote fear memories via the retrosplenial cortex, contributing to our fundamental understanding of remote memory function.