If you don't know anything about this please just read the first 20 lines on the below link and help me understand (I don't know anything either). The vapour liquid solid method: http://en.wikipedia.org/wiki/Vapor–liquid–solid_method uses a solid, liquid and gas phase to grow nanowires. While I understand the overall ideas I am unsure about some things. As far as I can see the idea is: Place a thin layer of an alloy on a substrate. Heat up until the alloy liquifies. At this point it will absorb some of the gaseous phase to form supersaturated droplets from which the nanowires are grown. But what exactly are the roles of gas/solid in this proces? Which of these phases supplies the atoms that form the nanowires. On the link both the solid and the gas contain Si, but it seems that it is the gaseous phase which the liquid catalyst absorbs and uses to grow the nanowire. So if this is understood correctly what is the role of the solid substrate?