The principles of chemistry have been used for the benefit of mankind. Think of cleanliness - materials like soaps, detergents, household bleaches, toothpaste, etc. will come to your mind. Look for beautiful clothes - immediately the chemicals from the synthetic fibers used to make clothes and chemicals that give colors to them will come to your mind. Food Materials - Again a series of chemicals that you have learned in the previous unit will appear in your mind. Of course, illness and disease remind us of medicines - again chemicals. Explosives, fuels, rocket propellants, building materials and electronics, etc., are all chemical. Chemistry has influenced so much in our life that we do not even realize that we are dealing with chemicals at all times; That we ourselves are beautiful chemical creations and all our activities are controlled by chemicals. In this Unit, we will learn the application of Chemistry in three important and interesting areas, namely: medicines, food materials and cleaning agents. Drugs are low molecular mass chemicals (~ 100 - 500u). These interact with macromolecular targets and produce a biological response. When the biological response is therapeutic and useful, these chemicals are called medicines and are used in the diagnosis, prevention and treatment of diseases. If higher than recommended doses are taken, most of the drugs used as medicines are potential poisons. The use of chemicals for the therapeutic effect is called chemotherapy,