A superprecise scalpel that can be used to operate on an individual cell is now a reality thanks to experimenters at Harvard University. “Ultrashort laser pulses [up to 1,000 a second] produce a spot as hot as the sun,” notes Eric Mazur, Gordon McKay Professor of Applied Physics. “Normally, that kind of heat would vaporize a cell, but it only shines for a millionth of a billionth of a second. The light intensity is very high, but the energy generated in such a short time can be compared to a mosquito bumping into your arm. A cell can easily take that.” A laser beam ordinarily travels right through a piece of glass or a transparent cell, but in this application it is focused into a very, very small space within a cell. “It’s like lighting a hot spark inside the cell without disturbing the surface membrane, the fragile bag that holds the cell together,” Mazur says. An exacting technique like this opens up a plethora of medical possibilities. The Harvard researchers vaporized a single mitochondrion, a minute biological motor that provides power to a cell to carry out its many functions. They cleaved a single nerve in a tiny roundworm, knocking out the creature’s sense of smell.