When did plants begin their symbiotic relationships with microorganisms? It is hypothesized that plant-microbe symbiosis began around 450 million years ago, when fungi known as endomycorrhizal fungi formed mutually beneficial interactions with early terrestrial plants [25]. At the time when early terrestrial plants evolved from aquatic photosynthetic organisms to adapt to life on land, nutrients were scarce, making symbiosis with nutrient-supplying microorganisms crucial for their survival. The symbiosis between plants and nitrogen-fixing bacteria emerged later, approximately 100 million years ago, and developed independently multiple times. For microorganisms, plants provided a convenient and safe habitat, while plants benefited by internalizing them, as this made it easier to manage and utilize microorganisms effectively.