People can have different blood types, known as blood groups. There are four main blood groups - A, B, AB and O. Each group can then be either RhD positive or negative, so your blood group can be one of eight types.
The genes you inherit from your mother and father determine your blood group.
Click HERE for more information from the National Health Service of the UK or view the video below:
Uploaded to youtube by ThePenguinProf on Feb 25, 2011