Light micrograph of cardiomyocytes (heart muscle cells). The heart muscle cells show many fine parallel fibres and intercalated discs (short squiggly light pink lines). The nuclei (dark blue circular structures) are slightly enlarged or hypertrophic, a result of chronic stress or damage on the heart. There is also fine yellowish lipofuscin pigment (small yellow-orange dots), a normal finding especially in older people. Haematoxylin and eosin stained tissue section. Magnification: 400x when printed at 10 cm.