If you take a small drop of blood from a finger tip and place it on a slide under a darkfield microscope you can watch patterns in the live-blood.
In standard microscopy light is shone directly through the sample (specimen) and viewed against a bright field or background.
However, we cannot easily observe live material in this manner, because a specimen must be thin to be observed, it is also virtually transparent. Therefore we must stain it to see it, and to do this we usually have to kill the specimen.
Red Blood Cells as seen in Darkfield
With darkfield microscopy, however, the procedure is crucially different. The light does not travel directly through the specimen, but comes in from the sides and only light which is reflected by the specimen is viewed and viewed against a dark background, hence “darkfield microscopy”. In this way a highly contrasted image is obtained and there is no need to use a stain. We can therefore watch living material.