Fibrin is a protein that plays a crucial role in the body's healing process. It is formed from another protein called fibrinogen, which is produced by the liver. When a blood vessel is injured, thrombin converts fibrinogen into fibrin, creating a mesh-like structure that helps to stop bleeding by forming a clot. This fibrin mesh traps blood cells and platelets, stabilizing the clot and allowing the healing process to begin. Over time, the clot is gradually broken down by another protein called plasmin, ensuring that the body can restore normal blood flow once the injury has healed.