Molecular imaging is a field of medical imaging that focuses on imaging molecules of medical interest within living patients. This is in contrast to conventional methods for obtaining molecular information from preserved tissue samples, such as histology. Molecules of interest may be either ones produced naturally by the body, or synthetic molecules produced in a laboratory and injected into a patient by a doctor. The most common example of molecular imaging used clinically today is to inject a contrast agent (e.g., a microbubble, metal ion, or radioactive isotope) into a patient's bloodstream and to use an imaging modality (e.g., ultrasound, MRI, CT, PET) to track its movement in the body. Molecular imaging originated from the field of radiology from a need to better understand fundamental molecular processes inside organisms in a noninvasive manner.Molecular imaging originated from the sector of radio pharmacology owing to the requirement to rise perceives the basic molecular pathways within organisms in a very noninvasive manner. Molecular Imaging emerged within the early ordinal century as a discipline at the intersection of biological science and in vivo imaging it allows the intellectual image of the cellular operate and also the follow-up of the molecular method in living organisms while not worrying them.