Explanation:

Researchers have developed the world’s first water-wave laser, demonstrating that lasers can be created by interactions between light and water waves.
A typical laser can be created when the electrons in atoms become 'excited' by energy absorbed from an outside source, causing them to emit radiation in the form of laser light.
For now, the water-wave laser offers a “playground” for scientists studying the interaction of light and fluid at a scale smaller than the width of a human hair.
In future, the laser could be used in tiny sensors that combine light waves, sound and water waves.