90% of the biomass on Earth is microscopic, so if we find life elsewhere it’s likely to be small. But even microscopic life can lead to big changes in a planet’s atmosphere, forming vast communities that work together to survive.

Microbial colonies like this one can be found all over Earth. Microbes in the top layers of the colony produce oxygen as a byproduct of photosynthesis, just like plants. Other microbes throughout the colony use oxygen for respiration. The layers visible in this jar are each dominated by different kinds of microorganisms. Together, they make up an entire ecosystem of producers and consumers of organic matter.

Bubbles of oxygen escape from the surface of the colony. Over millions of years, bubbles like these created the oxygen rich atmosphere that we breathe today.

You can make a community of microorganisms of your very own. Winogradsky columns like these develop from microorganisms that exist in mud almost anywhere you look. Winogradsky columns are created from organic-rich mud plus light and a food source, such as crumpled-up newspaper. Nature does the rest.

Inside a mature column, each layer is the address of a specific type of microbe that lives off the waste products of its neighbor and, in turn, gives off waste products that sustain life in another layer.