Opening credits. Scrolling text explains the history of mankind's research into blood. The narrator then explains what blood is with the aid of animations. He then talks about the 'modern discovery' of blood transfusion, beginning with the discovery of blood groups in 1901. The work of Karl Land Steiner in identifying the four blood groups is described with the aid of animations. His experiments are shown using animations, and the four groups are explained also with the aid of animations. The narrator explains that blood groups need to be considered when transfusing blood from one person to another.