na-adjective, noun
Describes something extremely small, visible only under a microscope, or relating to microscopic observation. Often used in technical or scientific contexts.
この生物は顕微なサイズで、肉眼では見えない。
This organism is microscopic in size and cannot be seen with the naked eye.
顕微鏡で顕微な構造を観察する。
Observe the microscopic structure with a microscope.
顕微鏡 is the common word for 'microscope', while 顕微 is the adjective/noun meaning 'microscopic'.
From 顕 (apparent, visible) and 微 (minute, tiny). The combination suggests making the minute visible, hence 'microscopic'.