I THOUGHT THE SCIENCE WAS SETTLED: An Unexpected New Lung Function Has Been Found – They Make Blood. “In experiments involving mice, the team found that they produce more than 10 million platelets (tiny blood cells) per hour, equating to the majority of platelets in the animals’ circulation. This goes against the decades-long assumption that bone marrow produces all of our blood components. Researchers from the University of California, San Francisco also discovered a previously unknown pool of blood stem cells that makes this happen inside the lung tissue – cells that were incorrectly assumed to mainly reside in bone marrow.”