Foelling, J., Belov, V., Kunetsky, R., Medda, R., Schoenle, A., Egner, A., Eggeling, C., Bossi, M. and Hell, S. W.
Photochromic rhodamines provide nanoscopy with optical sectioning. Angewandte Chemie International Edition 46: 6266-6270 (2007).

Switching individual photochromic and fluorescent rhodamine amides enable 3D far-field optical microscopy with nanoscale resolution, excellent signal-to-noise ratio, and fast acquisition times. The rhodamine amides can be switched on using two photons, which enables 3D detailed imaging of thick and densely stained samples (such as 5-μm silica beads and living cells) to be constructed.