Every day, it has been estimated, between one and five of your cells turns cancerous and your immune system captures and kills them. Think of that. 
A couple of dozen times a week, well over 1,000 times a year, you get the most dreaded disease of our age, and each time your body saves you.
Our bodies are a universe of 37.2 trillion cells operating in more or less perfect concert more or less all the time.
. . .
Ben’s field is orthopaedics, so he loves bones and tendons and cartilage the way other people love expensive cars or excellent wines. “See that?” he says, tapping a small, smooth, very white obtrusion at the base of the thumb, which I take to be a bit of exposed bone.
“No, it’s cartilage,” he corrects. “Cartilage is remarkable, too. It is many times smoother than glass: it has a friction coefficient five times less than ice.
“Imagine playing ice hockey on a surface so smooth that the skaters went 16 times as fast. That’s cartilage.
“But unlike ice, it isn’t brittle. It doesn’t crack under pressure as ice would. And you grow it yourself. It’s a living thing.”
. . .
“Bone is stronger than reinforced concrete,” says Ben, “yet light enough to allow us to sprint.” All your bones together will weigh no more than about 20 lb (nine kilograms), yet most can withstand up to a ton of compression.
“Bone is also the only tissue in the body that doesn’t scar,” Ben adds. “If you break your leg, after it heals you cannot tell where the break was. There’s no practical benefit to that. Bone just seems to want to be perfect.”
Even more remarkably, bone will grow back and fill a void.
“You can take up to 30 centimetres of bone out of a leg, and with an external frame and a kind of stretcher you can have it grow back,” Ben says. “Nothing else in the body will do that.”
. . .
Altogether, you are about 40 per cent muscle if you are a reasonably slender man, slightly less if you are a proportionately similar woman, and just keeping that mass of muscle uses up 40 per cent of your energy allowance when you are at rest and much more when you are active. Because muscle is so expensive to maintain, we sacrifice muscle tone really quickly when we are not using it.
Studies by NASA have shown that astronauts – even on short missions, from five to 11 days – lose up to 20 per cent of muscle mass. 
. . .
In the second or so since you started this sentence, your body has made a million red blood cells. They are already speeding around you, coursing through your veins, keeping you alive.
Each of those red blood cells will rattle around you about 150,000 times, repeatedly delivering oxygen to your cells, and then, battered and useless, will present itself to other cells to be quietly killed off for the greater good of you.
Altogether it takes seven billion billion billion (that’s 7,000,000,000, 000,000,000,000,000,000, or seven octillion) atoms to make you. No one can say why those seven billion billion billion atoms have such an urgent desire to be you.

— You Cure Yourself of Cancer 24 Times a Week … Without Knowing It
The Mail On Sunday | 21 September 2019 | Bill Bryson