Share 'Emulsifiers in chocolate'

These days it's not all that hard to find a bar of chocolate without some sort of emulsifier in it, the most common being lecithin. Emulsifiers' role in chocolate is to reduce chocolate's viscosity - to make it thinner in other words. Right. So that's what lecithin does. But, how do emulsifiers like lecithin work? What are they doing to the chocolate to thin it out?