OK, #mbnov word of the day is memory.
We are currently able to genetically engineer mice which neurons, when firing, produce a protein which responds to light. This protein works as a way to tag neurons which have been strongly activated.
Shining the right kind of light, we can re-activate the specific population of neurons activated by a given task, leading to the mouse experiencing a memory of the task itself.
Light-activated memories. It’s called optogenetics, look it up!