Medical imaging has significantly contributed towards providing capabilities for detection/diagnosis and monitoring of various diseases, by measuring changes associated with anatomical and molecular structures of underlying tissues in the human body. Recent advances in medical imaging has brought revolutionary changes for noninvasive detection and measurement of in vitro and in vivo tissue characteristic by utilising the optics, and such imaging techniques are considered as optical imaging. In optical imaging methods for biomedical engineering domain, visualisation details of internal tissues and organs can be done at levels as small as cells and molecules. This chapter focuses on biomedical optics, photon propagation in tissues, bioluminescence and fluorescence followed by the parameters and components required for optical imaging such as light sources, filters and detectors. In addition, microscopic imaging techniques for whole animal body imaging using optical imaging are discussed. In summary, it is concluded that optical imaging has the potential for detection and diagnosis of disease by looking at the anatomical as well as molecular details of the underlying body tissues. However, optical imaging is yet a vast field, from the understanding of effectiveness of the technique to analysis of the images.