Lysosomes are small vesicles, containing hydrolytic enzyme and surrounded by single membrane. They were discovered by de Duve but were named and observed by Novikoff. They are formed by Golgi apparatus and contain some 40 types of acid hydrolases for digestion of various materials.
Mitochondria (power house) were discovered by Kolliker in straited muscles of insects and given the present name by Benda. They are covered by a double membrane envelope. Outer membrane is permeable to many metabolite.
Nucleus (Robert Brown) is a double membrane covered protoplasmic body that contains hereditary material.
Chloroplasts are green plastids which take part in photosynthesis and temporary or permanent storage of starch. It is enveloped by double membrane, outer membrane is smooth.