In 1850, Kolliker for the first time see mitochondria. Later on C Benda coined the term mitochondria. These are the sites of cellular repiration, oxidative phosphorylation, synthesis of haeme protein cytochrome, myoglobin, etc.
Ribosomes are the sites of protein synthesis.
Chloroplasts are the sites of photosynthesis.
Golgi bodies help in cell wall formation (by secreting hemicellulose), enzymes formation, production of hormones (thyroxin), etc.