There’s a revolution in battery technology hiding in plain sight: The 3-D printing of batteries has the potential to put energy storage inside any device. This will enable lightweight and long-lasting consumer gadgets, long-range military drones and even nanoscale robots.

The way the world manufactures batteries has changed hardly at all in 30 years. Almost all the innovations we regularly hear about—from cheaper, tougher electric-vehicle batteries to “Holy Grail” solid-state batteries—are about changing the chemistry of batteries.

The promise of battery-tech 3-D printing (aka additive manufacturing) is simple: What if batteries could fill any available space, even structural elements of our gadgets, rather than always taking a rigid shape like a pouch or cylinder?

The new approach has obvious appeal. The entire airframe of a drone could be filled with energy storage for increased range. Smartglasses could have sleek battery-packed frames, so they look like everyday eyewear rather than “Revenge of the Nerds” props.

One of the biggest advantages of 3-D printing is that it works with any battery, regardless of its cell chemistry. It could advance today’s lithium-ion as well as emerging sodium-ion and solid-state tech.