There are more than 300,000 different kinds of plants spread across diverse environments, from arid deserts to lush forests. Having evolved about 700 million years ago, land plants have survived several extinction events that have decimated animal populations. And yet, plants lead deceptively simple lives. By just using water, air, sunlight, and nutrients, they make our world inhabitable. They take up water from the soil and carbon dioxide from the air, putting together sugars that form the foundation of the global food chain and belching out oxygen. This process is so central to plant identity that almost all the land plants use the same pores—called stomata—to regulate gas exchange.

Depicted as small mouths in the images, stomata are microscopic doughnuts that help plants breathe and control their moisture levels. The central circular pore is bound by two guard cells that can swell or shrink to open or close the pore. Slow your breathing, take a closer look, and marvel at innocuous openings that allow life as we know it to exist.