The concept of microbial life dates back to the 17th century, when pioneers like Antonie van Leeuwenhoek first observed microorganisms using a simple microscope. His discoveries led to the realization that the world was far more complex than previously imagined. This marked the beginning of microbiology as a scientific field, though it wasn't until the 19th century that figures like Louis Pasteur and Robert Koch made groundbreaking contributions, proving the role of microorganisms in disease and fermentation.
Microbes are incredibly diverse and can be found in almost every environment on Earth. Some live in symbiotic relationships with plants, animals, and humans, providing essential functions like nitrogen fixation or aiding in digestion. Others are pathogenic, causing diseases in both humans and animals, but they are just a small fraction of the total microbial world. In fact, microbes outnumber all other forms of life combined, with a single gram of soil or a drop of water containing billions of these tiny organisms.