Moroccan Hair Oil. You put a few drops on your wet hair and then blow dry. I was very unsure as I thought "oil = grease".
I could not be more wrong. It's miraculous. It makes hair super-shiny and no trace of oiliness. Obviously I bought some. It comes with a pump dispenser so you don't put too much on. I have since discovered that seemingly the entire internet is raving about it. Google it and you'll see what I mean.
Finally it seems it's good whatever your hair type - thick, thin, coarse, fine. Miracle product? Maybe. I shall keep you all posted.