The hexagonal phase is a special shape that things can take. It's like how you might have a round ball or a square block, but instead it's six-sided like a honeycomb. Some things that can take this shape are crystals, molecules, and even soap bubbles.
The reason it's called "hexagonal" is because it has six sides that are all the same length and angle, which means they're all shaped like a hexagon. It's a very symmetrical shape, which means it looks the same from all angles.
Scientists are very interested in the hexagonal phase because it's very stable and can be used to create things like nanomaterials, which are really tiny things that can be used in all kinds of cool technologies. By understanding how this shape works, scientists can come up with new materials and technologies that could help make our world a better place.