One Pulse Instead of a Thousand express
A laser hits the sample, and molecules inside start to vibrate. This vibration heats the material by tiny fractions of a degree. Previously, such heating was considered a nuisance, but now it's used to read chemical composition, like guessing who's coming down the hallway by the sound of footsteps.
The new optical microscope uses just one pair of laser pulses to trigger this heating. Conventional instruments fire thousands of pulses in a row, like knocking on a door many times, hoping someone will hear. Here, a single knock suffices. The laser is deliberately stretched in time so it hits more gently and doesn't damage living cells.
On living HeLa cells, researchers could spot patches of cholesterol in the cell membrane. Previously, these were labeled with glowing antibodies, but now they're visible directly, like grease spots on the surface of broth. The imaging speed is 10 frames per second, and the cell stays alive.
The heat left behind by a laser flash turns out to be a precise language of chemistry. One pulse, and the molecular map is ready.
A single laser pulse heats the sample by less than a thousandth of a degree, but that's enough to see individual molecules.
In the TV series "Fringe," characters use a device that "sees" the chemical composition of objects from a distance — the new microscope does something similar, but within a drop of solution.