What Determines Emergent Properties?

An emergent property is, by definition, something other than the parts that compose it. Liquidity and solidity and gaseousness are not inherently the properties of h to molecules. Neither is consciousness a in any way conceivable as a by product of just some neurons That you combine together. Ike even theoretically, i does it make sense? So how can that be? Another question is, what makes a thing a thing?