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microscopic mi·cro·scop·ic (mī'krə-skŏp'ĭk) or mi·cro·scop·i·cal (-ĭ-kəl)
Too small to be seen by the unaided eye but large enough to be studied under a microscope.
Of, relating to, or concerned with a microscope.
Being or characterized as exceedingly small; minute.