 - 英文怎麼說？

microorganism
We know about them because even we don't see it with naked eye, we still see it under a microscope.

2008-09-05 12:13:23 補充：
oh! I didn't see the chinese word in the topic.  should be "mite" or "tick"

How do you call these living organisms which you can't even see with you naked eye ?