Human Red Blood Cell

The oxygen courier making 300,000 round trips through your body/Microscopic Life

Red blood cells are biconcave discs just 7 micrometers across that carry oxygen from your lungs to every tissue in your body. Each cell contains about 270 million hemoglobin molecules, and your body produces roughly 2.4 million new ones per second. They lack a nucleus, which maximizes space for hemoglobin but means they cannot divide or repair themselves.