My friend Devin's essay, "Making Cellular Memories" just came out today in Cell (and it's open access!) It's a great look at how natural cells and synthetic biological systems use feedback loops in order to maintain memory of past events. Like whole animals, cells need to remember what happened to them before in order to respond appropriately to new signals. Synthetic biologists can use memory to track cells that have experienced a certain input in a heterogeneous population, and to activate different responses depending on the historical context.
In sum, both nature's wisdom and previously designed memory modules can provide bioengineering insight to accelerate our progress toward the creation of devices capable of producing cellular memories that can last a lifetime.
Overall, a great read and a fascinating topic!