TIL that we aren't single organisms, but walking ecosystems. For decades, it was believed that bacteria outnumbered human cells 10-to-1. Modern science has corrected this: the ratio is actually about 1.3-to-1. You are roughly 38 trillion bacteria and

A revised analysis estimates that a typical 70 kg adult human body contains about 30 trillion human cells and 38 trillion bacteria, challenging the widely cited 10:1 bacteria-to-human cell ratio. The study highlights that most bacteria reside in the colon, which dominates their total count in the body, while human cell counts are largely determined by hematopoietic cells. The total bacterial mass is estimated to be around 0.2 kg, and the bacterium-to-human cell ratio is closer to 1:1 than previously thought. This work provides fully documented calculations and updated quantitative understanding of cell numbers in the body.