Biomolecules are of great importance to medicine as therapeutic agents. There are innumerable resources for isolating and purifying new biomolecules from under the ocean, in land and genetically engineered microbes. The process for down-streaming the biomolecules involves a series of steps that isolate the molecule of interest with each step. The downstream differs with each of the above mentioned sources. Natural products isolated thus are of immense pharmaceutical interest. It also opens the way to identify new already existing biomolecules, rather than the tedious process of engineering microbes or higher beings to do so. We shall divide the downstream into parts based on the type of resource used to isolate the biomolecule of interest. We shall classify them as Natural products and expression of cloned genes. Natural Products can be isolated from either a plant or an animal or a microbe. While its easier to isolate natural products from plants and microbes, it is tedious to isolate natural products from animals. Isolation from animal sources or the like, must necessarily involve genetic experiments.