"We give them more, and then they can choose what they want to use. It is like the mobile phone ... it has many features, but most people use only one or two of them."

When you think about it, Donato Coco's metaphor is very apt. And when it comes to this Citroen designer's own recent programmes within that company, the idea has certainly been carried through into the cars.

He was responsible for the original Pluriel in 1999, a concept car that ended up 'driving off the stand' and onto the public roads this year. Many commentators question the relevance of the car, which in clever but rather gimmicky ways can be transformed into a saloon, a cabriolet, a spider or even a pick up.

So what? Nobody ever asked for a car that could be everything, surely? Coco is unapologetic.

"It offers more than other makers' products, and it also allows for a greater variety of ways to open to the sky than either a sunroof or a soft cover," he argues. "We could also have decided not to make the roof arches demountable, but we decided to go ahead with that anyway, because it allowed another option to the customer. Each can then make a choice as to how the car will be used."

So far, some 20,000 people across Europe have made the choice for Pluriel itself, and the company hopes to sell three times that a year when demand clicks into high gear.

But for another of Coco's 'babies', the target is significantly bigger, at 190,000 a year for the C2, the 3-door derivative on the same platform as the C3 and the Pluriel. This is another case of 'giving more choice', he says, emphasising that the C2 is NOT simply a 3-door C3, nor a direct replacement for the Saxo. In fact, a C1 joint venture smaller car with Toyota has just been signed off for production in 2005.

"The C2 is a new car in the segment, shorter and differently styled and aimed at buyers who are mainly young, fashionable, modern. I see it as a complete new product, very contemporary, for people who don't need much space in the back except to occasionally carry a couple of friends, but who want something that is very richly specified."

While the C2 has been deliberately styled to look small, Coco points out that in the front area is is in fact even wider inside than in the C3 with which it shares that part of the interior. It is in other parts of the package that there are attempts to find accommodation and luggage solutions. A cost question mark could be put on the decision to use a two-stage rear door opening, for instance, but he defends this on the fact that shopping can be dropped into the back of the car without needing the space to open a full hatch door.

"We have to be more imaginative these days when designing small cars. With the great increase in safety technologies, we have lost traditional storage spaces, and we must look for solutions that go beyond the design parameters of traditional cars."

Far from feeling stressed that more versions on even one car platform are currently being demanded by both carmakers themselves and their customers, Coco gives the impression that it is almost liberating. "I have managed programmes for larger cars, such as the Picasso," he notes. "But I like small car design, because it gives me and my colleagues the scope to be imaginative. Paradoxically, the 'space is more open' and there are more possibilities for expression."

For Mark Lloyd, Manager of Advanced Design at PSA Peugeot Citroen, the C-Airlounge concept car is not just a pretty thing designed to make photographers click on a motor show stand. It is the latest in a series of 'C' cars - Crosser and Airdream being the predecessors - with the aim of developing new 'languages' of form and function.

The C Airlounge showcases specific developments in interior design and external aerodynamics, both of which will find their way quickly into future cars. Both are aesthetically pleasing, though differently depending on whether you are a stylist or an engineer.

"With the interior we are devising a new form of 'sculpting' which is different from the rather cold Germanic-inspired style of contemporary cars and concepts," says Lloyd, who worked for Jaguar Cars in a previous employment. "We don't feel comfortable with all those controlled lines. They lack emotion and passion."

So, in an attempt to create emotion and passion, Lloyd and his team looked outside the industry for ideas that might help them in a specific objective of creating moods in a car with light. "We're learning a lot about light from other area, such as exhibition spaces and shop lighting, which can be very subtle."

But to light cars in new ways requires new technologies of lighting, and possibly the most spectacular of these in the Airlounge was a material woven from silk and very fine fibre-optic thread, used to decorate the inside of the doors of the car and allowing an almost infinite variety of light patterns and colours to be made. This joined the 18th and 21 centuries in the car.

"The material was woven for us in Lyons in France, the centre of silk haute couture, on an 18th century loom, which gave us a mixture of exquisite tradition and high technology. We used silk because it is a noble material and because Airlounge is a concept car we could afford to be a little extravagant. Though we would not use silk in a production car, the system provides us with possibilities to use new ways of improving the environment inside a car at night."

In another area altogether, the Airlounge gave Lloyd the opportunity to explore something from his own background, aerodynamics engineering, and at least two innovations here point the way to future advances even though they are unseen to the casual onlooker.

"Aerodynamics has been rather neglected in cars for ten or 15 years, and now everybody is up to the same standard as were the leaders then," he suggests. "But with more fuel consumption requirements for 2008, it is one of the areas where much can be achieved."

In Airlounge, one non-mechanical idea has improved airflow around a traditional bottleneck in this area, the impact of air on a wide tyre. Strategic redirecting of high-pressure air has created a 'curtain' which shields this impact zone. At the rear of the car, an innovative system of tiny moveable 'blades' is helping to deal with a problem of drag on the curved back upper bodywork caused by the 'streaming' of moving air into high- and low-pressure systems. As Lloyd explains them, the solutions are as elegant as is the overall look of the car itself.

In the past, concept cars were little more than imagination allowed run rather riot, merely models to make the onlookers go 'wow!' But no more, and today's concept car designers are very much only a wheel revolution ahead of what will be standard in the cars we all drive tomorrow.