Do you know about nanobots? Nanobots are tiny robots that are small enough to be injected directly into the blood stream through a syringe. Once they are circulating around our bodies suspended in our blood plasma, they can analyze the "what's what," as the youngsters say, with our cells and membranes and tissues and so forth. If they find a problem, they can self-replicate many copies of their teensy-weensy little selves to correct the problem.
Look! Tiny little robots! They're so adorably cute, and they're helping my red blood cells somehow. I love them!
Right now, nanobots are only theoretical. (Or, if you're a conspiracy theory enthusiast, that's what the Dark Overlords want you to believe, anyway. That nanobots haven't already been injected into our bodies when we got our flu shots last November, I mean. Now they're continuously transmitting our personal health data back to the motherships hovering in clandestine orbits above us. Just think about it, naive reader.)
Even though they're only theoretical, nanobots are incredibly interesting! Just ponder the possibilities!