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Macrophage engulfing bacteria as part of the immune system's response to infection. SEM X9000 #0039868300 | 188894.jpg

Credit: POWER AND SYRED/SCIENCE PHOTO LIBRARY Caption: Tomato stem. Coloured scanning electron micrograph (SEM) of the stem of a tomato plant (Lycopersicon lycopersicum).

Neuron cell body (purple) with numerous synapses (blue). Communication from one neuron flows to another neuron across a synapse, the small gap separating neurons. SEM X80,000.

The human eye viewed from inside, showing the iris, the ciliary body, and the edge of the pupil (SEM).

The cytoskeleton is made of strings of proteins that constantly stretch and shrink as the neuron sends out projections toward other neurons, making and breaking connections. This neuron is from mouse hippocampus, a part of the brain important in memory, but the ones in the human brain are constructed much the same way.