Clinical pharmacology is the science of drugs in humans and their optimal clinical use in patients. It is underpinned by the basic science of pharmacology, with an added focus on the application of pharmacological principles and quantitative methods in the real human patient's population. Clinical pharmacology is a branch of biomedical science. It includes drug discovery, the study of the effects of drugs on their targets in living systems and their clinical use, as well as the study of biological function related to these chemicals. Clinical pharmacology includes the application of pharmacological principles, such as pharmacodynamics and pharmacokinetics. Clinical pharmacologists are physicians, pharmacists, and scientists whose focus is developing and understanding new drug therapies. Clinical pharmacologists work in a variety of settings in academia, industry and government. In the laboratory setting they study biomarkers, pharmacokinetics, drug metabolism and genetics. In the office setting they design and evaluate clinical trials, create and implement regulation guidelines for drug use, and look at drug utilization on local and global scales. In the clinical setting they work directly with patients, participate in experimental studies, and investigate adverse reactions and interactions. Clinical Pharmacology, in theory, has been practiced for centuries through observing the effects of herbal remedies and early drugs on humans. Most of this work was done through trial and error. In the early 1900s, scientific advances allowed scientists to combine the study of physiological effects with biological effects. This led to the first major breakthrough when scientists used clinical pharmacology to discover insulin. Since that discovery clinical pharmacology has expanded to be a multidisciplinary field and has contributed to the understanding of drug interaction, therapeutic efficacy and safety in humans. Over time clinical pharmacologists have been able to make more exact measurements and personalize drug therapies.