What is Blood?
Micorscope View: Although blood appears to be red liquid it is actually composed of a yellowish liquid called plasma and billions of cells. The vast majority of these cells are red cells and these give blood its red color. Besides the red cells, the blood also contains several types of infection-fighting white cells and tiny cell fragments called platelets which are essential for clotting.

Scanning EM View: These cells have been electronically colored to show up in this photo from a scanning electron microscope (EM). The red cells are shown in red, the white cells in yellow and the platelets in green.

Photo: Copyright Dennis Kunkel, University of Hawaii