This lesson provides an overview of the concept of activation energy and how enzymes lower it, thereby providing the means for exquisite control over what happens in our bodies. It covers the basic mechanisms of enzyme regulation with a few examples and explains the strengths and limitations of each mode of regulation. It does this through the lens of answering the following question: given the second law of thermodynamics, why does any order remain in the universe? Why don’t we and everything else fall apart?