Hubrecht Institute-Royal Dutch Academy of Science and University Medical Center Utrecht 2 articles published in JoVE Medicine Ex vivo Live Imaging of Lung Metastasis and Their Microenvironment Renske J.E. van den Bijgaart*1, Niwen Kong*1, Carrie Maynard1,2, Vicki Plaks1,3 1Department of Anatomy, University of California, 2Hubrecht Institute-Royal Dutch Academy of Science and University Medical Center Utrecht, 3Department of Cell and Developmental Biology, Sackler Faculty of Medicine We describe a relatively simple method for ex vivo live imaging of the tumor cell-stroma interactions within lung metastasis, utilizing fluorescent reporters in mice. Using spinning-disk confocal microscopy, this technique enables visualization of live cells for at least 4 hr and could be adapted to study other inflammatory lung conditions. Developmental Biology Generation of Aggregates of Mouse Embryonic Stem Cells that Show Symmetry Breaking, Polarization and Emergent Collective Behaviour In Vitro Peter Baillie-Johnson1, Susanne Carina van den Brink1,2, Tina Balayo1, David Andrew Turner1, Alfonso Martinez Arias1 1Department of Genetics, University of Cambridge, 2Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences We have developed a protocol to generate aggregates of mouse embryonic stem cells that display self-organization, symmetry breaking and elongation paralleling axial development. This technique allows the study of axial developmental processes and the generation of cell types that are otherwise difficult to perform in monolayer culture.