And this takes place within these adipose cells, fat cells of our body. So let's suppose that we just woke up and after waking up, we basically want to go for a run or a swim. So we want to carry out some type of exercise. Now, overnight, what happened was the cells of our body used up their supply of glucose and glycogen. And so as soon as we go for that morning run or swim, our cells will depend on triglycerides to actually form the ATP molecules that are needed to carry out those particular cell processes. And so the question is, what actually initiates the breakdown and the mobilization of triglycerides within our fat cell in this circumstance?