OPT-ical Tomography for Developmental Biologists

Almost unidimensional in their primordial existence as single cells, multicellular organisms quickly develop into complex 3D architectures and machineries composed of multiple cells and tissues. For more than a century, classical microscopy has given us important insights into the mechanics and mechanisms that bring about complex biological forms during their development, but it was only recently that we have been able actually witness those processes it their full complexity and wonder. This was due mainly to the emergence of 3D optical microscopy techniques, such as confocal or two-photon, and more recently of mesoscopic imaging such as light-sheet and optical tomography. I will quickly review some of the principles behind optical tomography/slicing and its use in cell and developmental biology and focus on optical projection tomography (OPT) as a tool for embryologists used to characterize vertebrate embryonic and fetal anatomy with little efforts and great fidelity.