If you had breast cancer, and you were able to shrink yourself, travel inside your body, where all the cells were people, animals, plants, all life forms. What would it look like?
You would want to look to some invasive group of cells. Some flora and fauna are invasive, taking over native cells, a beautiful yellow flower, the Centaurea solstitlialis, so pretty, but invasive, overcoming all the native grasses in Oregon. A weed that hides behind the yellow petals. The someone-let-go-Piranha in America, eating all the native fish in a river, and your soft testicles if it gets lucky. Invasive cells, species are all over the world. Sometimes perfectly acceptable in their own habitat. But, talking about humans and the evil cancer lurking inside human bodies, it will be people who are the threat, not a fish or a plant. Not all people of course. No, not a majority even, though it could seem like it, but this is truth, cancer is what it is. It is a life-form of cells that wants to kill you eventually, destroy its very own host! Where will you find them? Everywhere, except I suspect they will not be working out, not focused on maintaining life-energy, as what would be the point? The ones on the treadmills, or in Eastern Philosophy Yoga, are not what I would guess the type. But of course there will be a few, sentinels sent out, spies. Why does it want to consume you, kill you? That seems illogical, pretty darn stupid, but you know it is true. So they do whatever they can to remain undetected by your body, or…you, as it infiltrates you, and so if you based a conclusion on whom is good, nice, seemingly no harm to you, it would be dangerous. Cancer is a fiend that carefully hides, sends out its cells everywhere in its host, your solitary system. It will be not obvious to you it is a threat until it has spread. So your worst enemy may be seemingly not. Be wary of smiles, be wary of everyone. And get an bad ass Angel to watch your back!