Energy usage and biclops lasereyes.
The old wive’s tale of dental fillings picking up terrestrial radio signals. Satellite military communications frequencies.
Quantum and DNA computing. Synesthesia. Recognizing that we are all synesthetes within the bounds of “normal” human brain operations.
Extra- super- ultra-dimensionality. Flatland again.
“Beings of light” and why this might be the most reasonable example of the trope. The world on the other side.