Is There a Difference Between the Inside and the Outside of a Cell?

Every single cell is a battery, which we didn't appreciate until the 1970s. Cells are studded with little pores and these are called ion channels. They let in sodium and potassium ions preferentially because of the way they're kind of like bouncers slash VIP entrances. And so because of these preferences, the inside of the cell is always kept at a more slightly more negative value than the ions that sort of swim around in the soup outside of the cell. When the balance outside shifts, a bunch of these little pores, bouncers freak out and open the emergency exits.