Old embryos are now being looked at in a new way. About a hundred years ago, an embryologist by the name of FranMyn Paine Mall devoted his career to collecting human embryos and fetuses (an embryo becomes a fetus after 2 months of gestation) from miscarriages and abortions. These specimens form the core of what is known today as the Carnegie Collection of Human Embryos, housed in the National Museum of Health and Medicine of the Armed Forces Institute of Pathology in Washington, D.C. Whereas this is a priceless national educational resource, how do we extract the information about our embryonic development from these specimens? Classic techniques involve slicing a specimen as thinly as possible on a microtome, then reconstructing the slices in a model large enough to study. The problem is the specimen is effectively destroyed in the process. What is needed is a technique that allows whole embryos to be examined, but not destroyed.