A high power field, or HPF, refers to a single field of view under a microscope, usually under the highest magnification (400x). This field of view represents a tiny section of the whole microscope slide/tissue that’s being examined, but at this high magnification you can see different structures and cells that can be counted. This is usually used as a way to diagnose a condition from a tissue biopsy.
The image below shows a slice of a mouse lung under a microscope, with the boxed section magnified 400x. The magnified section is the HPF and in it I circled 3 cells that are staining pink as an example. If we were counting these cells, this would represent 3 of these cells per HPF.
Synonyms:
high power field, HPF