Organ (anatomy)
In biology, an organ is a group of tissues that work together in an organism. They specialise in particular vital functions. They create an organ system which, as a whole, is an organism.
These are examples of organs:
Classification
Organelles > Cells > Tissues > Organs > Organ systems > Organism
Organ (anatomy) Media
The liver and gallbladder of a sheep
Strobilus of Equisetum telmateia