English: This composite image was created in recognition of The Society of Photo-Optical Instrumentation Engineers (SPIE) designation of 2015 as the “International Year of Light.” Medical imaging scientists and engineers contribute to the quest for the improved human condition by providing imaging that spans the entire usable electro-magnetic spectrum (seen at bottom). From the humblest of beginnings with simple magnification of objects and focusing with lenses, to the biological observation of cells with rudimentary microscopes in the visible spectrum, medical imaging today has both extended away from the visible spectrum towards longer and shorter wavelengths (low and high energies) and exploited the hyperspectral nature of the visible which was once considered “commonplace” or rudimentary. Considering yet a different cross-section through the various imaging modalities across the spectrum, the medically useful information gained spans anatomic, physiologic, and molecular regimes. Systems and algorithms have been developed as single-modality acquisition systems, and also as multiple-modalities with conjoint reconstruction, each informing the other in the quest to optimize image quality and information content. In addition, the role of light-based technologies in enabling advanced computations in tomographic reconstructions, computer-aided diagnosis, machine learning (neural networks, deep learning, etc.) , and 3D visualizations as well as in data-enriched storage of medical images has further extended the potential knowledge “seen” through imaging. The breadth of the electromagnetic spectrum offers limitless opportunities for improvement and inquiry, in our quest to answer human life’s difficult questions. This montage was first published on the cover of the SPIE’s Journal of Medical Imaging (July-Sept. 2015, vol. 3, no. 3) and is but a small tribute to the multitude of medical imaging scientists who have contributed to the wealth of new knowledge as we interrogate the human condition. The gray-scale whole body images (from Left to Right) are acquired from longer wavelength modalities to shorter wavelength modalities spanning the (currently) usable electromagnetic spectrum. The background images include: a coronal Magnetic Resonance Image (MRI) T2 weighted image slice, a posterior surface Infra Red (IR) heat map, a coronal non-contrast Computed Tomography (CT) slice, and a coronal 18F-fluoro-deoxyglucose Positron Emission Tomography (FDG-PET) slice. The selection of color inset images includes (from Top-to-Bottom, then Left to Right): [1] diffusion tensor magnetic resonance imaging (MRI) used to image long white matter tracts within and around the human brain illustrating neuronal connectivity (coloring refers to bluish=vertical direction; green=horizontal A-P direction; red=horizontal lateral direction) (courtesy of Arthur Toga, PhD); [2] registered and superimposed coronal proton-MRI (gray-scale) and a hyper polarized 129Xe ventilation MRI scan (color scale) within the same patient’s lungs, prior to their receiving a bronchial stent (courtesy of Bastiaan Driehuys, PhD); [3] coronal slice through a microwave-based image reconstruction of the Debye parameter ε (epsilon) in a heterogeneously dense human breast phantom (courtesy of Susan Hagness, PhD); [4] juxtaposed optical image of the retina and vertical and horizontal Optical Coherence Tomograph (OCT) slices showing pigmentosa retinopathy (courtesy of Jean-Michel Muratet, MD); [5] functional 3-D photoacoustic imaging of melanoma (gray scale) in vivo, surrounded by highly optically absorptive blood vessels (red) (courtesy of Lihong Wang, PhD); [6] optical micrograph of HeLa cells stained for microtubules (blue) and co-stained with DAPI for actin visualization (red); HeLa cells are the world's first stem cell line, originally derived from the aggressive cervical cancer cells of Henrietta Lacks (courtesy Tom Deerinck/NCMIR); [7] visualization of the pelvis highlighting the colon, which is imaged with contrast x-ray computed tomography (CT), and after digital surface rendering can be used in virtual colonoscopy, thus avoiding a physical visible light-based colonoscopy; [8] registered and fused sagittal 99mTc-sestamibi dedicated molecular single photon emission computed tomography (SPECT, heat color scale) and low-dose CT slice (gray scale) of a patient’s uncompressed, pendant breast containing two surgically confirmed DCIS loci in the posterior breast (courtesy of Martin Tornai, PhD); [9] classic, early x-radiograph of Wilhelm Röntgen’s wife’s hand (adapted from http://en.wikipedia.org/wiki/100_Photographs_that_Changed_the_World); [10] transverse pelvic CT (gray scale) with multiple superimposed simulated x-ray photon radiotherapy beams, and their cumulative 20Gy (red) deposited dose isocontours at the focus of a tumor (courtesy of Paul Read, MD, PhD); [11] false-colored scanning electron micrograph of human immunodeficiency virus (HIV) particles (yellow) infecting a human H9 T-cell (turquoise) (adapted from http://biosingularity.com/category/infection/); [12] transverse 18F-dopa positron emission tomography (PET) slice through a Parkinson patient’s brain showing decreased in vivo quantitative uptake in the right caudate and putamen (courtesy of Christaan Schiepers, MD, PhD); [13] registered and fused transverse head CT (gray scale) and registered superimposed PET image (color) of a patient immediately after radio-therapeutic proton irradiation showing endogenously created 15O-positron emitter (2 min half-life) within the nasopharyngeal tumor focus (courtesy of Kira Grogg, PhD). [14] transverse (long axis) cardiac 99mTc-sestamibi SPECT slice illustrating thinned myocardial apical wall in a procedure performed thousands of times daily around the world (adapted from www.medscape.com). These images are but a small sampling of the breadth of the spectrum of light that is currently being investigated the world over by passionate scientists and engineers on a quest for the betterment of the human condition. All contributors for these images used herein have given their permission for their use, and are graciously thanked.