stromatolites

Stromatolites are layered, rock-like structures formed by the activity of microorganisms, mainly ancient cyanobacteria. These bacteria trap and bind sediment particles and secrete minerals as they grow, creating characteristic layered formations. Found in some modern environments like shallow marine waters, stromatolites are among the Earth's earliest evidence of life, dating back over 3.5 billion years. They played a crucial role in shaping the planet’s atmosphere by producing oxygen through photosynthesis, marking a significant step in the development of complex life.