PRESERVED EARLY HUMAN FETUS (64 days postconception) has been imaged by magnetic resonance microscopy (MRM) and by traditional light microscopy (small inset above). At this stage, the embryo is about 30 millimeters long. Computer visualization techniques can render selected parts of the embryo translucent while leaving others opaque. By adjusting the opacity of the specimen in this manner, researchers can see internal structures at varying depths and in their natural context without damaging the specimen (a–c). Scientists can also zoom in on, rotate or back away from the embryo (d–f) or use a visualization procedure called segmentation to focus on specific organs, such as the developing lungs (g–k). f g