The basic principles of organometallic chemistry will be discussed in this course. The modern chemistry is merged into one from classical organic chemistry and traditional inorganic chemistry. We will shed light on activation of small molecule by metal-ligand complex. We will discuss the stepwise mechanism of insertion of metal into organic molecules and elimination by different pathway. Only catalytic amount of metal can produce the large number of molecules those include drug, natural products, pharmaceuticals, our daily needs, etc. in gigantic quantity.