False-colour transmission electron micrograph (TEM) of a single human lymphocyte, the smallest of the white blood cells. The central nucleus (orange brown) is slightly indented & the chromatin (genetic material - DNA) is moderately condensed; the darker coloured chromatin is seen towards the nuclear wall. The cytoplasm (green) is sparse, but contains a few mitochondria; these small brown, cigar-shaped bodies are the sites of energy production & storage within the cell. The outer plasma membrane supports a few microvilli (projections). Lymphocytes undergo transformations when activated in their role in immunological defence. Magnification: x3000 at 35mm size. Reference: MICROCOSMOS, figure 6.2, page 109.