Instagram. It's a thing. A young people's thing. The last time I looked, it was all Parisian pastel macaroons and gilded teenagers paddleboarding on Lake Tahoe.
But, hand on heart, that was 2014, when my elder daughter was 12 and preoccupied with both of the above.
In the intervening years, she's moved on. So has Instagram. And now, belatedly, so have I.
This week, the scales have fallen from my eyes, shattered into a million pixels. Far from being the online equivalent of a teenage magazine, a shared scrapbook of moments and thoughts with a smattering of aspirationally attractive role models, Instagram harbours sinister secrets and cynical fakery.
Self-harm imagery. Bleak nihilism. The normalisation of self-hatred. The "inspirational" quotes giving voice to suicidal intent.
By comparison, the covert advertising of gym equipment or high-end fashion peddled by social media celebrities pales into if not quite insignificance then a different category of immorality.
I shall return to the careless deceits of product placement later because, at present, it's the images of 14-year-old Molly Russell that keep replaying in my mind. Molly's beautiful face, glowing with innocence, with potential. Her father, Ian, talking about the incalculable depth and breadth of his devastating loss and the role Instagram played in the tragic suicide of his shining daughter in 2017.
"Some of that content is shocking in that it encourages self-harm, it links self-harm to suicide," he said. "I have no doubt that Instagram helped kill my daughter."
Facebook, which owns Instagram, has said it is "deeply sorry" and that graphic content that sensationalises self-harm and suicide "has no place on our platform".
I've just downloaded the app, and I'm baffled as to where the red line between "sensationalising" and merely graphically posting about self-harm and suicide lies.
In a few keystrokes, I found stomach-churning pictures with quotations like "There's a voice in my head says I'm better off dead" and the insidious "Suicidal people are just angels who want to go home".
One person's overblown angst is another's incentive; awful doesn't begin to describe what's freely available on the app. There are occasional "trigger-warning" alerts but, frankly, they just signpost the way to pages guaranteed to affirm feelings of isolation and worthlessness.
I'm not saying that mental health issues shouldn't be aired on social media - far from it. But let them be discussed responsibly, not with noir photographs with the caption: "It's weird how, in a matter of seconds, you could just become a memory."
Young people who pore over Instagram have no idea who's actually leaving messages. They probably never once pause to consider the real identity of the other users; in the social media world you're either an influencer or a nobody.
At least influencers are finally being brought to heel after an investigation by the Competition and Markets Authority.
Sixteen celebrities including Ellie Goulding, Rita Ora and Zoella have agreed to change how they post online. From now on, they will clearly state if they were paid to promote a brand or product.
Presumably, others will follow suit. I'd love to know how so many Love Island starlets can afford those luxury winter holidays and designer bikinis they keep sharing.
The power of influencers on our teenagers can't be underestimated; young people gravitate towards their own tribe. Short of locking our offspring in an ivory basement (towers have excellent 3G...), all we as parents can do is hope they choose their role models wisely, ie not on the basis of their bank balance.
British-born multi-millionaire Stephanie Scolaro, 26, whose previous claim to fame was being one of the Rich Kids of Instagram, was this week found guilty of importing 17,000 worth of hats and bags made from endangered python skins dyed in lurid colours.
Sentencing her to a 160-hour community order, Judge Michael Gledhill QC was scathing about Scolaro, from Marylebone.
"All her life, she has in effect been given exactly what she wanted," he said. "There is no thought about pythons in Indonesia. How they are skinned alive and how they are endangered doesn't cross her mind."
To a great degree, his summing up described the ultimate social media star.
"This is a young woman who, for all sorts of different reasons, is utterly self-centred," he added. "Her entire life concentrated around herself."
It would serve as a cautionary tale, were it not for the fact that most of our young people don't have 17,000 to spare, and if they did, they sure as heck wouldn't spend it on garish, ghoulish, cruelty assured accessories.
My elder daughter will soon turn 17 and, her early Zoella crush long forgotten, turns up her nose at influencers. Her younger sister is 10 and hooked on Roblox, a multiplayer online game that resembles Lego, but as yet has no interest in social media for social media's sake.
As she grows in maturity (aka becomes afflicted with self-consciousness), she will no doubt gravitate towards Instagram in search of that aforementioned tribe.
When she does, I hope to high heaven it will have cleaned up its act entirely. I will be watching. Not through any personal desire to catch up on Rita Ora's career, but because it would be a dereliction of my parental duty not to know who my daughter is with when she hangs out online.
The Daily Telegraph, London