Barcelona - Ferrari's ability to challenge Lewis Hamilton and Mercedes' dominance of Formula One will be examined as the longest season in the sport's history gets underway with the first series of testing in Barcelona on Monday.
Hamilton is looking for a third consecutive drivers' championship and the fourth of his career across a mammoth 21 Grand Prix season that starts in Australia on March 20.
The Englishman coasted to the title last season as he and Mercedes teammate Nico Rosberg won 16 of the 19 races.
However, Ferrari showed signs of a revival with four-time world champion Sebastian Vettel claiming the other three race wins, exceeding team principal Maurizio Arrivabene's pre-season expectations.
Arrivabene is now looking for even more progress from the SF-16H to be able to challenge Mercedes with Vettel and Kimi Raikkonen -- the last man to win a drivers' title with Ferrari back in 2008 -- at the wheel.
"I think this year, we need to push a bit more. We would like to fight until the end for the championship," Arrivabene said at the SF-16H launch.
"I know that is not going to be easy, because our competitors are not sleeping, but we are committed to do our best."
Mercedes certainly believe Ferrari will be their main obstacle to another season of dominance.
"We see Ferrari as our main threat and it remains to be seen how we position ourselves in the weeks to come," Mercedes technical director Paddy Lowe told Sky Sports.
"Ferrari are a very strong competitor and one we worry about. It keeps us motivated to keep us pushing all the time."
Worryingly for Mercedes' competition, though, the double world champions ran a trouble free 98.2km on a filming day in the W07 Hybrid in Silverstone last week.
"We take our opposition very seriously -- especially Ferrari," said Rosberg.
"They are going to be a big threat so we need to keep pushing."
Elsewhere, all eyes will be on what improvements the McLaren-Honda partnership has developed in the off-season after a disastrous return to F1 for the Japanese manufacturer last season.
Former world champions Fernando Alonso and Jenson Button didn't even get on the podium as McLaren finished ninth in the constructors' championship ahead of only Marussia, who failed to register a single point.
Red Bull will also be looking for continued improvement as they ended 2015 promisingly to finish fourth in the constructors' championship.
"We're looking to build the progress we made at the end of the season and carry that momentum into the early races," said team principal Christian Horner.
However, it was Williams who were the best of the rest behind Mercedes and Ferrari last season and are looking for more in 2016 with the partnership of Finland's Valtteri Bottas and Brazilian Felipe Massa back for a third consecutive season.
"Staying where we are will be a challenge in itself, but we are determined to keep improving because only winning will ever be good enough," team principal Frank Williams said at the launch of the FW38.
The grid extends to 22 cars in 2016 as thanks to the introduction of the first American F1 team in 30 years in Haas.
Meanwhile, French car giant Renault returns as a constructor after buying out the financially stricken Lotus team.