Merriam-Webster Collegiate Dictionary - micr-

 or micro-  combining form  Etymology: Middle English micro-, from Latin, from Greek mikr-, mikro-, from mikros, smikros small, short; perhaps akin to Old English smealic careful, exquisite  1.  a. small ; minute microcapsule  b. used for or involving minute quantities or variations microbarograph  2. one millionth (10-6) part of microgram  3.  a. using microscopy microdissection ; used in microscopy  b. revealed by or having the structure discernible only by microscopic examination microorganism  4. abnormally small microcyte  5. of or relating to a small area microclimate  6. employed in or connected with microphotographing or microfilming microcopy