Photonic Crystal

Consider the following statements:

1. Recently, researchers from the Centre for Nano and Soft Sciences (CeNS) have developed soft tunable photonic crystal with enhanced thermal stability and optical purity.
2. The crystal reflects vivid colours in the visible spectrum and has potential applications in making more durable and better reflective displays and laser devices.
3. Photonic crystals are optical nanostructures in which the refractive index changes periodically.

Which of the above statement(s) is/are true?