Organelle

Schematic of typical animal cell, showing subcellular components. Organelles: (1) nucleolus (2) nucleus (3) ribosome (4) vesicle (5) rough endoplasmic reticulum (ER) (6) Golgi apparatus (7) Cytoskeleton (8) smooth ER (9) mitochondria (10) vacuole (11) cytoplasm (12) lysosome (13) centrioles

In cell biology, an organelle is one of several structures with specialized functions, suspended in the cytoplasm of a eukaryotic cell. Organelles were historically identified through the use of microscopy, and were also identified through the use of cell fractionation.

A few large organelles probably originated from endosymbiont bacteria:

chloroplast
Other plastids, such as leucoplasts, amyloplasts, Etioplasts, Elaioplast, rhodoplasts, and chromoplasts.
mitochondrion

Other organelles include:

acrosome
centriole
cilium/ flagellum
endoplasmic reticulum
glyoxysome
golgi apparatus
lysosome
melanosome
myofibril
nucleus
parenthesome
peroxisome
ribosome
vacuole
vesicle

Other related structures:

cytosol
endomembrane system
nucleosome
microtubule
cell membrane