Concept cars are a window into the future of a brand's model line. And, while they almost always look nothing like their eventual production descendants, they're always great fun.

The unique unveilings at this year's Frankfurt motor show were no exception, with a wild array of interesting concept cars on show.

Here, we've listed our five favourite concepts from the world's biggest motor show.

5. Mercedes-Benz IAA Concept

This concept from German manufacturer Mercedes-Benz is called the IAA. While it stands for Intelligent Aerodynamic Automobile, it shares its initials with the Frankfurt motor show (Internationale Automobil-Ausstellung).

This stunning machine actually changes shape, beyond 80km/h, to increase efficiency. Perhaps a sign of where Mercedes-Benz will head with future cars? Read more about the Mercedes-Benz IAA Concept here.

2015 IAA September 17 - 27, 2015, Frankfurt, Germany

4. Hyundai N 2050 Vision Gran Turismo Concept

This futuristic racing concept debuts Hyundai's performance N brand and shows that Hyundai could one day too compete in something like a Le Mans race. Just like the Bugatti Vision Gran Turismo Concept below, it's a computer-based racing car brought to life.

It would be cool to see Hyundai draw from some of the lines on this concept car in their production line. Read more about the Hyundai N 2050 Vision Gran Turismo Concept here.

Hyundai N 2025 Concept - 2015 IAA September 17 - 27, 2015, Frankfurt, Germany

3. Nissan Gripz Concept

Every word is cooler with a 'z' in it, right? Sort of. Thankfully the Nissan Gripz Concept makes up for it with a cool Juke-esque design that is said to be an insight into its future performance range.

The brand wants to move away from a low-slung sports car into more of an SUV shaped one. The Japanese company suggests that it's not a Juke or Qashqai replacement, making it a unique model if it makes it into production. Rear more about the Nissan Gripz Concept here.

Internationale Automobil-Ausstellung, Frankfurt-9243

2. Bugatti Vision Gran Turismo

The Bugatti Vision Gran Turismo has made it into two of our top five lists — also appearing in the top five supercars of the Frankfurt Motor Show. It's only fitting that it also sits here.

This incredible looking concept is a vision into the Veyron replacement, but, as it stands, it forms a life-sized version of the car that lives in the Gran Turismo game. Read more about the Bugatti Vision Gran Turismo Concept here.

Bugatti GT Concept - 2015 IAA September 17 - 27, 2015, Frankfurt, Germany

1. Porsche Mission E Concept

Mission E or Mission Tesla? The Porsche Mission E Concept is the brand's all-electric sports car set to tackle the huge insurgence from Tesla in the automotive market.

The Porsche concept not only looks stunning but points to a long-range electric vehicle that will no doubt have the sporting credentials to match. It also features hand-gesture communication controls that could trickle down into future Porsche models. Read more about the Porsche Mission E Concept here.

Internationale Automobil-Ausstellung, Frankfurt-9488