Blood clot. Coloured scanning electron micrograph (SEM) of a blood clot from the inner wall of the left ventricle of a human heart. Red blood cells (erythrocytes) are trapped within a fibrin protein mesh (cream). The fibrin mesh is formed in response to chemicals secreted by platelets (pink), fragments of white blood cells. Clots are formed in response to cardiovascular disease or injuries to blood vessels. Connective tissue (orange) is also seen.
Ruptured venule. Coloured scanning electron micrograph (SEM) showing stacks (rouleaux) of red blood cells exposed inside a torn venule. A venule is a very small blood vessel in the microcirculation that allows deoxygenated blood to return from the capillary beds to the larger blood vessels (veins). Red blood cells are the most abundant cell in the blood. They have no nucleus and are about 7 micrometers across. Magnification: x2300 when printed at 10 centimetres wide.
Ruptured capillary. Coloured scanning electron micrograph (SEM) of a red blood cell squeezing out of a torn capillary. A capillary is the smallest type of blood vessel, often only just large enough for red blood cells to pass through. Red blood cells (erythrocytes) are biconcave, disc-shaped cells that transport oxygen from the lungs to body cells. Credit: STEVE GSCHMEISSNER/SCIENCE PHOTO LIBRARY
Coloured scanning electron micrograph (SEM) of rods (blue) and cones (red), the light sensitive cells in a human retina. Rods aid vision in dim light, while cones allow colour vision | Ralph C. Eagle, Jr. | SCIENCE PHOTO LIBRARY
Brain tumour. Coloured scanning electron micrograph (SEM) of a glioma, a type of tumour that arises from glial cells of the central nervous system. The most common site for gliomas is the brain. They can be either low or high-grade, with the latter having the worse prognosis. Magnification: x8000 when printed at 10 centimetres wide. Credit: STEVE GSCHMEISSNER
Colored scanning electron micrograph (SEM) of squamous cell carcinoma (cancer) cells from a human mouth. The many blebs (lumps) and microvilli (small projections) on the cells' surfaces are typical of cancer cells.