Feynman, in his Lectures on Physics, gives a succinct description of physics: "Physicists always have a habit of taking the simplest example of any phenomenon and calling it “physics,” leaving the more complicated examples to become the concern of other fields — say of applied mathematics, electrical engineering, chemistry, or crystallography [or biology].”. What then, is the physics of life? And, given the complexity, where do we start? 

In this talk, I will try to make a case for studying the physical basis for metabolism, the veritable engine of life. I will go through one of the very few quantitative "laws" in biology -- the so called Kleiber's law -- relating metabolic activity with organismal body mass. The data spans roughly 20 orders of magnitude ranging from a single mitochondrion to the largest mammals in a power-law relationship. After detailing some theoretical frameworks to understand this data and also their shortcomings, I will briefly describe our own proposal and efforts in this direction.