A fat droplet inside a living cell is like a bobber in rough water. It doesn't move in a straight line but in jerks, sometimes pausing, sometimes speeding up. Previously, such movements could only be seen in a single plane, like watching the bobber from above without knowing its depth. Now scientists have built a camera that captures the entire volume of the cell at once, like a 3D movie, at 19 frames per second.
The camera's secret lies in combining infrared light with a standard light microscope. The infrared beam slightly heats the molecules, causing them to expand. This expansion is detected by the visible light, revealing where different substances are located. Previously, this method was slow: obtaining a single volumetric frame took a second or more. The new approach speeds up imaging by nearly 400 times.
With the new camera, scientists tracked the paths of fat droplets in three dimensions and found that their motion doesn't resemble ordinary random walking. Inside the cell, there are hidden "tracks" and "obstacles" that are invisible in a flat view. The method also allows capturing a chemical spectrum over a wide range in a second, like not just taking a photo but distinguishing all the ingredients of a dish without tasting it.
Such a tool opens the door to observing living cells in real time: how they divide, how they respond to drugs, how they restructure their internal architecture. The bobber no longer hides in the depths.
A fat droplet in a cell can move faster than you blink: in one second, it travels a distance comparable to its own size.
In the film 'Innerspace', characters travel inside the human body — the new microscopy makes such journeys a reality for scientists, except instead of a submarine, there's a laser beam.