A new era of Formula One racing began on Monday when grand prix teams returned to action to begin work on the 2009 season at the Barcelona circuit.
New aerodynamics regulations, as well as the use of slick tyres, will make for very different cars, something that was already evident when the first hybrid machines took to the track this morning at the Spanish circuit.
Teams will also be testing, or at least simulating, the KERS device, which will also be used next season.
The BMW Sauber team, already using a 2009 aero package, had all eyes on them after the most striking car came out of their garage early in the morning.
With an almost retro-looking flat nose and front wing, the car was markedly different from its previous version.
The German squad, first with test driver Christian Klien and then Robert Kubica at the wheel, are also running their KERS system, which they had already tested on track before.
The Williams team are also running part of their 2009 aero package, with a 2008 front and next year's rear.
World champions Ferrari will have two cars on track, one of them with the 2009 aero package and one with this year's settings. The former was also fitted with ballast that simulates the weight of a KERS device.
McLaren are also working on their KERS system, with Pedro de la Rosa running it in a version of this year's car.
Tyre supplier Bridgestone has taken two different compounds of slicks for the test, although teams are limited to just four sets of the harder option.
Most team have between 10 and 20 sets of tyres available to them.
Today's test is also seeing five-time world rally champion Sebastien Loeb taking to the wheel of a Red Bull F1 car alongside grand prix drivers.