It is every boy's first toy, handily packed into your lap and thrust into the world with you when you're born. As you both grow, it morphs from mystery to mastery, becoming your primary driver at times and, in your teenage years particularly, the place where your mind resides.
So to look down at your crotch and see something that looks like it's been in a horrific car accident that the rest of your body somehow avoided was as upsetting, for me, as watching a close friend get badly beaten. Possibly more so.
Ever since waking up from my vasectomy I have tried to picture what my surgeon got up to while I was out. Mostly I see him standing on the operating table with a seven iron and a vicious glint, but sometimes he's holding a bowling ball.
I don't regret my choice to be sedated, of course, because for me there was no choice at all (despite the fact that around 60 per cent of men are, apparently, tougher than I and endure their vasectomies using just local anaesthetic and gritted teeth).
Partly this is because the sight of blood effects me the same way as gargling effluent, but it's more to do with the gut-curdling tale of a former colleague who crawled into our office a few days after his procedure looking like he'd been murdered and then revived.
He'd opted for the local, which had unfortunately worn off at a critical juncture, causing him to flail about, screaming, as a nurse attempted to hold him down. Rarely has the question 'would you like some more drugs?' been more warmly welcomed.
With war stories like that, it's hardly surprising that many men have mastered the art of putting off having "the snip" (and what an insufferably poetic euphemism that is; you snip flowers not cherished body parts).
My doctor, Justin Low, a man so passionate about his work at Marie Stopes that he's known as "the ball whisperer", tells many alarming tales of blokes who confess to him that they've had two or three more children than they'd planned to, because they just couldn't talk themselves into having the vasectomy they'd told their wives would be no problem.
Then there are those who make it all the way into his surgery before suddenly getting up and bolting, sometimes wearing nothing but a surgical gown and a look of terror.
Dr Low and I talked a lot about fear before my procedure, which he says is the main thing keeping men from "taking one for the team", as he likes to call it.
Firstly, there's the illogical fear - that you somehow won't be a man any more if you remove your ability to procreate - and then there's what I call the perfectly reasonable fear, that even if you are knocked out for the downstairs disturbance, the pain, swelling and immobility afterwards will be too excruciating to bear.
The psychological fear of mangled masculinity didn't touch me at all, or not until the dreaded morning arrived and I was saying goodbye to my two young children, and it struck me that this was it, I'd never get to make any more of these little miracles. I found thinking about dirty nappies at this point very helpful.
The good news is that the actual vasectomy process is easy and painless, except for the night before when you have to deforest an area of your body that may never even seen a razor before. I found this about as easy as shaving a couple of prunes in a Glomesh purse, with hair growing out of it (the nurses advise you to ask your wife for help, but you wouldn't ask it of your worst enemy).
The less good news is that the recovery is unpleasant, and at times alarming, although you do discover that, while black is not officially a colour, it can contain many and myriad shades of purple and violet.
The pain is not, however - and this is very important to remember - anywhere near as bad as recovering from child birth.
The strange affection you develop for bags of frozen peas only lasts a few days, happily, as does the ribbing from your wife, who enjoys pointing out that you finally look like an underwear model.
All any men who are worrying over whether to get the chop or not need to know is that I rang my former colleague who'd had the horrific experience to ask how he felt about his vasectomy now, years later, and he described it as "the best thing I've ever done".
Clearly, he needs to get out more, but the point is that the benefits, in the end, far outweigh the discomforts, and frankly, now that everything is back to its normal colour, I'm a little embarrassed that I cried so much about it.