By Billie Rubin, reporting from the labs of Stanford Blood Center
Here's a great picture of red blood cells, platelets, fibrin, and a white blood cell making a clot. There's a lot of activity that goes on in a little cut. The pretty cell in the middle is the white blood cell, waiting to pounce on any bacteria that sneak in through a cut in your skin. You can't see the platelets well in this picture but they are in there, sticking together with the fibrin to make a sort of scaffold that traps red cells. Together they all form the clot and keep your blood nicely contained.