1. National Physical Laboratory, TW11 0LW Teddington, UK
2. Department of Paediatrics, Wellcome-MRC Cambridge Stem Cell Institute, University of Cambridge, Cambridge, UK
3. Leibniz Institute of Photonic Technology, Albert-Einstein-Straße 9, 07745 Jena, Germany
4. Institute of Physical Chemistry and Abbe Center of Photonics, Friedrich-Schiller-University, Helmholtzweg 4, Jena, Germany
5. CRUK Cambridge Research Institute, Robinson Way, Cambridge CB2 0RE, UK
6. Faculty of Physics and Astronomy, Friedrich-Schiller-University, Jena, Germany
7. Micron Advanced Bioimaging Unit, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK