If you shrunk to the size of a single cell, the world would be unrecognizable. You might be in water, but swimming would get you nowhere. There might be food around, but reaching would push it further away. And you would not have a brain — after all, brains are billions of cells, but you would be just one cell. And yet, single cells have devised ingenious ways of discovering, interacting with, and thriving within their world. In this lecture, I will describe new ways of moving, eating, and thinking that are unfamiliar to us but work just fine at the scale of a cell. I will discuss how basic physics constrains these ways of living, and how cells can get around these constraints by joining together into multicellular groups. Cell-scale physics reveals the ingenuity of evolution and offers a new perspective on survival, disease, and the transition to multicellular life.