It is his family that keeps the visionary physicist’s feet on the ground. His wife is an ambitious physician at the university clinic, so the domestic routine must be well organized. Every morning, he takes their four-year-old twins to kindergarten. And thanks to the pestering of the two boys, he regularly revisits an old passion – the saxophone. While he was in Finland, Hell took lessons in jazz and improvisation. He would like to spend more time making music – if only he had the time. Running is another thing that Stefan Hell does less often than he would like. But the family has been kept on its toes for a few months now anyway, thanks to its latest addition, a baby daughter.
Not to mention another recent offer from abroad. In spring 2008, Stefan Hell got an offer to move to Harvard. “Of course it was a great honor, and it really wasn’t easy for me to decide,” he admits. “A new building, fantastic academic environment, top people, top students – it was very, very attractive. But in the end, the opportunities I have here at Max Planck tipped the balance.”
And so it was that Stefan Hell and his family recently flew, not to America, but to Finland. In Turku, his old domain, he received an honorary doctorate – in true Finnish style, wearing a doctor’s cap and a sword of sharply honed steel. Even his former boss was visibly moved. “In those critical early days, the Finns had confidence in me,” says Hell with gratitude. “They saw the potential, and they saw a man with the energy to realize it.” Maybe the steel sword that Stefan Hell brought back from Turku is not a bad symbol of his career, and of the will to slay a scientific dragon.
A new wave is emitted from every point in a light wave, for instance when it hits the edge of an object. That is why, under an optical microscope, two objects cannot be distinguished if they are less than half the wavelength away from each other.
A beam of light scans a sample. A pinhole in the optical path blocks image information from outside of the focal plane – the depth of focus is higher than that of a conventional microscope.
Two opposing confocal microscopes reduce the oblong focal point of a single microscope to a sphere (4Pi refers to spherical geometry).