Emperipolesis is when one cell decides to invite another cell over for a sleepover. It's like asking your friend to come over and hang out with you for a while.
But instead of just hanging out, the invited cell gets all cozy inside the host cell, like snuggling up in a big blanket. The host cell makes sure the invited cell is comfy and safe by surrounding it with special structures.
During this sleepover, the invited cell can share things with the host cell, like special proteins or other important stuff. And sometimes, the host cell can use the invited cell's help to do important jobs, like healing or fighting off bad germs.
Eventually, the invited cell goes back to its own home, and the host cell goes back to its own business. But the experience of emperipolesis can help both cells in lots of ways, like making new friends or getting stronger.