Introduction: Cellular Structure and Function
All organisms are made of cells. Complex organisms (such as humans) are made up of collections of highly specialized cells, each with its own specific function. Different types of cells have evolved specific shapes and properties which help them do their jobs inside the organism.
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Human white blood cells
As part of our immune system, white blood cells such as these move toward sites of infection.

Elapsed time, 20 minutes.
A drop of blood was placed on a coverslip with a silicon spacer and diluted with saline solution. The drop was incubated at 37°C for 20 minutes, then red blood cells were washed away. A mixture of saline solution with human serum was used to cover the remaining cells. Images were taken on an upright inverted microscope with a 40x DIC objective at room temperature using a digital camera.