Just to clarify, optically recording neural activity from ensamble of cells ("thoughts") has been done in neuroscience for many years using voltage / glutamate / calcium indicators + imaging. CNiFER is a breakthrough is because it provide ways to measure the "hormone" of brain, these are often molecules in tiny amount that modulate how cells in an area fire.

A not-so-good analogy is before we can measure electrical current in wires, now CNiFER allows us to measure electromagnetic field. This will help to explain why some headphones nearby will beep when your cellphone received a message.