Even without understanding the science of blood, we recognize that blood pumping through our bodies is an indicator of life itself. In movies and real life, we understand that blood outside the body means someone may be injured or dead.

In this unit we describe the components of blood, the proteins that determine blood type, and how transfusion (sharing) of blood between people is possible.

• What is blood?
• What are blood types?
• What are blood transfusions?

Funding provided by a Howard Hughes Medical Institute Precollege Science Education Initiative for Biomedical Research Institutions Award (Grants 51000125, 51000176)