Place cells in the hippocampus encode the location of animals in the environment. Any given place cell becomes active only when we are in a specific spatial location (indicated by red in the shadow or "place field" of the cell represented here). Populations of place cells can fully represent the space around us, and they become active in sequence as we move through space. Cells like this allow us to navigate in the environment, to plan and figure out new trajectories, and provide the contextual information that forms the basis for episodic memory.