Plural of granum; in plant biology, stacks of flattened, disc-shaped structures (thylakoids) found in chloroplasts where photosynthesis occurs.
From Latin 'granum' (grain), plural 'grana'; applied to these structures because they resemble tiny grains when viewed under an electron microscope.
Inside every green leaf, grana are the tiny factories running one of Earth's most important chemical reactions—converting sunlight into chemical energy that feeds almost all life on the planet.
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