I. Jahresfeier am 30. Mai 2015

in my life: Dr. Thomas Jovin, the Managing Director of the Max Planck Institute
for Biophysical Chemistry in Göttingen at the time, had become aware of my ac-
tivities. An accomplished and open-minded scientist with American background,
who successfully kept abreast of the latest developments in molecular biology, che-
mistry, and optics alike, convinced Erwin Neher, Herbert Jäckle, Peter Gruss, Jür-
gen Troe, and the other directors of the Institute to invite applications for setting
up a small group in modern microscopy for a five year period. They had Winfried
Denk (then at Bell Labs) or me in mind. In the spring of 1996 I spoke to Winfried
on the phone. When he said he wasn’t interested, it came as a big relief, because I
had good chance of prevailing against the other applicants.
In the meantime, we had made progress with STED microscopy in Turku.
After testing a few dye Solutions in a cuvette with Ignacy Gryczynski of Joseph
Lakowicz, group in Baltimore that showed some fluorescence modulation, I found
out that one could apply a heavily chirped titanium sapphire laser to turn off a
dark red fluorophore (with the trade name Pyridin2) under microscopy conditions
almost completely This was not easy to work out, because unlike in a cuvette, in a
microscopy sample, stirring is not an Option to get rid of radicals and bleaching, and
the intensities are by Orders of magnitude higher. It was also difficult to demon-
strate the resolution increase directly because Pyridin2 could not be coupled to
biomolecules. Fortunately, it occurred to me how it could be it done indirectly:
slightly offsetting the STED beam with respect to the excitation beam was expected
to reduce the focal fluorescence region to subdiffraction dimensions. Translation
of a confocal point detector across the image plane then proved that this reduction
indeed occurred. From that point, I knew that STED microscopy would work-
at least under certain conditions. I didn’t write this up because I thought that it
wouldn,t convince the critics and end up in a low-rankingJournal again. However,
in January 1996, I showed the result at the Friday physical Colloquium in Heidel-
berg, where I gave a talk in front of my formet professors including Otto Haxel,
Franz Wegner, Joachim Heintze, and Dirk Schwalm who asked questions at the
end. It was my habilitation lecture, and habilitation was important to carry on in Sci-
ence and supervise one’s own diploma and PhD students (officially). Until then,
Professor Cremer was supportive by taking care of the formalities. Today, I am very
grateful that I was allowed to habilitate in Heidelberg despite the fact that all the
relevant work was done in Turku.
In December 1996 I took up the position in Göttingen. It was just in the nick
of time, as the money from Wallac Oy had run out. The Max Planck Institute
in Göttingen was incredible because, for the first time, I was able to plan a little
ahead and submit my own research proposals. I submitted a grant for STED to an
agency of the German Federal Ministry of Research, which was promptly rejected.
However, the officials in charge accepted my appeal and approved the grant against
the experts, recommendations. Shortly thereafter, Thomas Klar applied to work as

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