He, or she, has the potential to make you angrier than you ever imagined you could be, more depressed than you could have contemplated, and (this more than anything) more frustrated than you'd have believed possible. But they are also, at times, funnier, noisier, more fulfilling and more exacting than any other experience. The vital thing to know about parenting teenagers is this: they still need us, their mums (and dads).
They're learning to live without us, but as they travel down that path - whisper it where you will - they actually need us more than ever.
But however aware you are of the theory, the practice of living with teenagers is almost inevitably going to be a rollercoaster ride.
Teenagers - not any teenager, of course, but your teenager - will plunge you to depths you never thought existed before. Teenagers are hard work - and anyone who tells you otherwise is either lying, or isn't doing the job of raising them very thoroughly.
Don't expect them ever to admit to it (probably, they don't even know themselves how much they care about what you think) but knowing it is fundamental to everything you do as a parent.
And, of course, if it's getting a bit much, share your parenting teens travails on Talk.
None of us can stay tied to the apron strings for ever - you didn't, I didn't, and our kids won't either.
Take a look at Mumsnetters' advice on guiding your child through their hectic teen years and out into the big wide world.
US, All Rights Reserved has no association with the links on its site and holds no responsibility for their content. We use our hosted galleries,movies and other hosted material, which provide a 2257 link at the bottom of each page.
Our partners are fully compliant with the 2257 regs.
In the long term, naturally, they will learn to do everything they need to do without us; but right now, in the learning phase, we have a tremendous influence to bring to bear, and a huge amount to offer.
While adolescents might pretend for all they're worth that they don't give a fig for what you or their dad thinks about anything, the truth is that they do give a fig - in fact, they give several hundred.