A blood clot forms when your blood coagulates - when it goes from a liquid to a solid.  You can see this happen when you have a cut – at first, there is a lot of blood but sticky platelet cells help to stop this and make a scab.  When the skin has healed, that scab falls off and your defences are back to full strength! 

Click on Find Out More to learn how your body uses blood clotting to defend itself!