How do our brains make sense of a space? People have used the stars and constellations to navigate great distances for centuries, but only recently have we discovered that this concept applies to how we naturally and unconsciously process our surroundings. When you first enter a room, Grid Cells lay down a carpet of equilateral triangles. As you walk through that space you pass from one triangle to the next; your brain keeps track of exactly which triangle you are in.
Border Cells fire as you approach a boundary, for example a physical wall or a steep drop like a train platform.
You continue to walk and as you turn your head to the right or left, a new Head Direction cell fires. These cells activate only when your head points in a specific direction and help to keep you oriented so you know where you are in the grid.
Your brain starts to fill in the grid as you walk further into the space. Place Cells are dropped at specific locations like pins on a map: the front door, the shoe box, the light switch at the end of the hallway. These locations, and events that take place at these locations, are stored as memories in our brains. When these spaces are visited for a second time, all of these cells fire together to create the idea of that space. It is not hard to see the analogy between these cells and stars in the night sky. Both appear as a jumbled mess but by imposing an arbitrary order, we can make sense of them and use them to navigate the world around us.