For billions of years life on Earth was restricted to aquatic environments, the oceans, seas, rivers and lakes.
Then 450 million years ago the first plants colonised land, evolving in the process multiple types of beneficial relationships with microbes in the soil.
These relationships, known as symbioses, allow plants to access additional nutrients. The most intimate among them are intracellular symbioses that result in the accommodation of microbes inside plant cells. A study recently published describes the discovery of a common genetic basis for intracellular symbioses.