Iatrochemistry (or chemical medicine) is a branch of both chemistry and medicine (ἰατρός (iatrós) was the Greek word for "physician" or "medicine"). Having its roots in alchemy, iatrochemistry seeks to provide chemical solutions to diseases and medical ailments.
Astrochemistry is the study of the abundance and reactions of molecules in the Universe, and their interaction with radiation. The discipline is an overlap of astronomy and chemistry. The word "astrochemistry" may be applied to both the Solar System and the interstellar medium. The study of the abundance of elements and isotope ratios in Solar System objects, such as meteorites, is also called cosmochemistry, while the study of interstellar atoms and molecules and their interaction with radiation is sometimes called molecular astrophysics. The formation, atomic and chemical composition, evolution and fate of molecular gas clouds is of special interest, because it is from these clouds that solar systems form.
Petrochemistry is a branch of chemistry that studies the transformation of crude oil (petroleum ) and natural gas into useful products or raw materials. These petrochemicals have become an essential part of the chemical industry today.