i pakai example eh..
emulsion tu mcm liquid foundation. Bnyk ingredients campur2 tapi kalo u tak touch d liquid for a long time, nanti liquid tu leh settle into many layers of ingredients. So mcm liquid foundation, nanti u nampak powder kat bwh, pas tu tgh is d water, then atas minyak.
serum nie usually less ingredients and concentrated... n usually they are clear... kalo leave untouch, the ingredients tak separate...
dats y serum usually more expensive than emulsion.