To push beyond the foldscope-eye limits try to team it with a high definition smart phone. A RBC is shaped like a mint lifesaver. The outer edge is thicker than the middle. When viewing with the smart phone zoom in to reveal the 2-micron edge. The normal RBC can be distinguished from an abnormal one. A WBC is about 24-microns, and depending on the shape you can make out the various WBCs, T-cells, and B-Cells. WBCs are about 1% of the total blood. The purpose of blood is to feed body cells and remove wastes while fighting off foreign viruses.
The study of blood is Hematology. a link is provided.