This image from a blood smear shows a typical small lymphocyte. It consists of a circular nucleus that is darkly stained because most of its chromatin is in a condensed form (heterochromatin). The cells has only a thin rim of cytoplasm, which, as seen here, is often stained blue. The cytoplasm usually lacks granules, although some larger lymphocytes, which are probably killer T-lymphocytes, have a few large cytoplasmic granules.

Stain = Wright's Blood Stain.