In biology, particularly cell biology, the term organelle is used to describe any one of a number of types of subcellular structures, historically identified through the use of some form of microscopy.
A few large organelles probably originated from endosymbiont bacteria:
... households, and 4,197 families residing in the town. The population density is 1,058.4/km² (2,740.4/mi²). There are 5,574 housing units at an average density ...