Blood is made up of the following:
The hemoglobin in red blood cells gives blood its red color. Red blood cells carry oxygen from the lungs to your body's organs and tissues and take carbon dioxide back to your lungs to be exhaled.
Platelets are very small colorless cell fragments in your blood whose main function is to stop bleeding.
Plasma is the liquid portion of your blood. Plasma transports water and nutrients to your body's tissues. Plasma also contains many proteins that help the blood to clot and fight disease.
White Cells or Leukocytes
White cells fight infection.
Want to know more about blood? Here are Fifty Blood Facts
(Source: America's Blood Centers - americasblood.org)