A special types of crystal that can hold large amounts of information.
Photonic Crystals have metal elements within them, that arrange to metallic, dielectric structures. This caused them to be able to hold large amounts of energy and/or information.
- Ice Lords: This was the bases of their technology
- Axion: It's internal main crystal was composed of this.
- Spark Holders: Safely carrying a spark
- Based of the item from Transformers IDW