Ionic crystals are formed through the combination of positive and negative ions.

Photonic crystals are widely used in optical devices.

I have a collection of positive crystals.

I collected several rock crystals during my trip to the mountains.

The twin crystals were found in the cave.

Time crystals are a new and exciting area of research in physics.

I love the texture of cheese crystals in aged cheddar.

I have a collection of lead crystals on display in my living room.

Phononic crystals are materials that can control and manipulate sound waves.

Ferroelectric crystals exhibit unique electrical properties.