This new marketing term has been coined by television executives to describe the 10-to-16 year olds who have outgrown cartoons and Teletubbies and have resorted to watching adult programmes because there is nothing on TV for them.
The task of entertaining tweenies falls to Andi Peters, the friendly face of children's television, who has recently been hired to run Channel 4's children and young people's programmes. "My brief is tweens, to move on, so programmes have an edge," he said. "The word 'youth' I don't like... I'm very conscious that kids like brands which are cool."
Indeed, as children strive to be cool, new evidence from Britain's leading youth and children's research organisation reveals that, by the age of 10, they can no longer be described as "children". One in four 11 to 12- year-olds admit drinking alcohol and more than half of 13-to-16 year olds know someone who takes drugs.
A Channel 4 spokeswoman said: "Tweenies describes a band of people who are not children, but are not old enough to enjoy adult programmes. They are somewhere in between: kids who aren't quite grown up, and aren't quite little, who are interested in more than mindless games and willing to be entertained at a slightly more intelligent level."
The so-called tweenie zone is between 6 and 7pm and some weekend slots - times when mainstream channels have less scope to dedicate airtime to such a specific age bracket. But Channel 4 is less constrained and is able to make programmes for niche audiences such as tweenies.
Mr Peters wants to make live programmes which react to the day's news: "Programmes that kids will talk about." He is a big fan of Channel 4's Wise Up, a sharp, Sunday morning programme which shows children how to deal with issues,'' he says. "It will give me the opportunity to work very closely with scheduling and create a brand. A lot of people don't know about Channel 4 programmes for children and young people. We can't even decide on the right title, yet."
So what should Mr Peters be coming up with? According to research published last week by ChildWise Monitor, the UK's leading youth and children's research organisation, The Big Breakfast is "huge" among tweenies and they most enjoy watching soaps. Three programmes are watched regularly by tweenies, according to ChildWise Monitor: Friends, Top of the Pops and The Simpsons. More than one in three of them watch the X-Files, Shooting Stars and Casualty. One in three watch The Bill regularly, but only three per cent choose it as their favourite. Friends is their favourite programme, watched by 57 per cent of them, followed by Top of the Pops (47 per cent), The Simpsons ( 45 per cent), and Shooting Stars (38 per cent).
More than 90 per cent of tweenies watch programmes after the 9pm watershed at weekends. During the week, 70 per cent of 11 to 12-year-olds watch after the watershed, and 90 per cent of 15 to 16-year-olds. Within tweenies, there are further divisions in terms of interests, as the ChildWise Monitor report reveals. Junior tweenies (nine-to-12 year olds) are most likely to participate in sports and other after-school activities. For them, the parent is a taxi driver, conveying small groups of Brownies, footballers and dancers to and from local halls - although they are not yet using their home as a hotel.
Junior tweenies are also the biggest computer-game playing age group. Many know contemporaries who smoke, and one in four drinks alcohol. Most of them disapprove of drugs.
Tweenies, it appears, are interested in news. Madeline Wiltshire is series producer of First Edition, a Channel 4 current affairs programme shown on Saturday mornings, which does well against cartoons. She believes there is a strong market for programmes which "show children how to be individuals".