For example, we said that the majority of the reactions that take place in nature and specifically in our body take place in water. So water is the universal natural solvent and the properties of water can influence the reaction pathway as we'll see in just a moment. We also spoke about thermodynamics and how in any reaction we always have to remember that that reaction has to obey the laws of thermodynamics. So it has to obey the first law of thermodynamics that basically states that energy is never created, energy is never destroyed. Energy can only be transformed from one form to another. So the total amount of energy in our universe is always constant.