1. J. Hwang, T. S. Ramalingam, M. Edidin, Department of Biology, The Johns Hopkins University, Baltimore, MD 21218, USA.
2. L. K. Tamm and C. Böhm, Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA.
3. E. Betzig, AT&T Bell Laboratories, Murray Hill, NJ 07974, USA.