Autobiography Stefan Hell

a doctoral Student in my laboratory. Thomas grasped the STED concept quickly
and was exceptionally talented. Combined with the much better equipment now
available, in a few months we reproduced and outperformed the initial experi-
ments carried out in Turku by far. 4Pi microscopy has meanwhile yielded com-
pelling images, too. In 1999 Stefan Jakobs joined in as the first biologist postdoc,
greatly extending the group‘s interdisciplinary expertise. He had realized that the
resolution was undergoing a transition and was attracted by the idea to pioneer its
use in the life Sciences. We were thus able to show beyond doubt that the resoluti-
on of far-field fluorescence microscopy can be drastically improved, and also used
in biological imaging.
In 2000 I married my wife, Anna, a pediatric orthopaedic surgeon at the Göt-
tingen university hospital, whom I had met in Göttingen in 1997. We now have
three children: Sebastian, Jonathan, and Charlotte.
In 2002, after several offers from other institutions, I accepted an offer to set
up a department at the Göttingen Max Planck Institute. Since 1994 it had been
clear that any reversible transition between a bright and dark molecular state is a
possible candidate for overcoming the diffraction limit. And everyone in my labo-
ratory was instructed to keep eyes open for unexpected ways to turn fluorescence
on and off. From 2003, setting up a Max Planck department gave me the possibi-
lity of adopting a more systematic approach, i. e. employing other state transitions
such as cis-trans isomerisation and synthesising the respective fluorophores, such
as switchable ones. I expanded the laboratory to include organic chemical synthesis
and together with Stefan Jakobs I added a project for switchable fluorescent pro-
teins. Thus, the basic idea behind STED and the metatstable state switching could
be successfully expanded to encompass other state transitions and low light level
Operation (RESOLFT). After 2003 I also set up a small group at the German Can-
cer Research Center (DKFZ) in Heidelberg to give researchers in this field direct
access to high resolution microscopy.
There were still hurdles to overcome and there were setbacks, too. But most
of the problems could be solved one by one - or the technological developments
around us worked to our advantage. Thus, we produced the first nanoscale far-
field immunofluorescence images (with Marcus Dyba), and demonstrated that
lens based microscopy with nanoscale resolution gives new insights in biology,
(e. g. with Katrin Willig, Silvio Rizzoli, Robert Kellner). In this context, I am par-
ticularly grateful to my colleague Reinhard Jahn and Stephan Sigrist, now a pro-
fessor in Berlin, who came up with interesting biological questions. At the end of
2006, the development of the first commercial STED microscope was completed.
It is now offered in several variants by three competing Companies, among others
by a start-up grown out of my group. Also in 2006, subdiffraction fluorescence
microscopy received an enormous boost from the seminal work of three American
groups that presented a powerful method switching molecules on and off indi-

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