Migrating cancer cell. Coloured scanning electron micrograph (SEM) of a cultured cancer cell moving (metastasising) through a hole in a support film. Numerous pseudopodia (arm-like), fillipodia (thread-like) and surface blebs (lumps) can be seen. These features are characteristic of highly mobile cells, and enable cancerous cells to spread rapidly around the body, and invade other organs and tissues (metastasis).
Graphene is different from most crystalline materials because its electrons are governed not by the standard Schrödinger equation, but instead by the Dirac equation of relativistic quantum mechanics. Dubbed a Dirac semimetal, its electrons travel effectively as massless particles, which allows them to reach much higher speeds than ordinary electrons – as high as 106 m s–1. As a result, the electron mobility in graphene is about 200,000 cm2/Vs, compared with about 1400 cm2/Vs in silicon.
Phagocytosis. Coloured scanning electron micrograph of a polymorphonuclear white blood cell or leucocyte, attacking Bacillus cereus bacteria. The leucocyte (orange), part of the body's immune system, is attaching to and engulfing the Bacillus cells (blue, rod- shaped). It uses enzymes to digest the bacteria. This process of engulfment and digestion is known as phagocytosis. Highly mobile, phagocytic cells migrate to areas of tissue damage.