Welcoming the reborn Mini in 2002, Americans couldn’t wait to pinch its adorable cheeks. “Look how tiny!” they cooed, plunking down cash and taking their baby home.

The Mini isn’t new and novel anymore, not with cumulative sales of more than 550,000. And while the third-generation 2014 Hardtop is still cute, it looks a bit chubbier. The British-built, BMW-designed coupe has expanded to manage people and cargo better. The new Mini is markedly more deluxe, powerful and fuel-efficient.

The maturation process will continue late this year, when a new Hardtop 4 Door (6.3 inches longer than the Hardtop coupe) reaches showrooms. That 2015 model seems a shrewd expansion of the lineup, perfect for people — including parents with actual babies — who’ve wanted a Mini but found it too cramped.

The Hardtop 4 Door will be substantially smaller than the chunky Mini Countryman. That all-wheel-drive crossover, along with the convertible and other variants, have not been updated with the new chassis and powertrains. And the three-door Clubman bids adieu.

The Mini helped to convince Americans that a small car could be worth relatively big money, and BMW’s designer fingerprints are all over the latest model. The new Mini’s front-drive chassis will underpin BMW-branded cars, including the 2 Series Active Tourer plug-in hybrid that will arrive next year.

The Mini adopts turbocharged BMW engines for the first time, in a car that previously relied on Chrysler and then Peugeot Citroën power plants.

For the base Cooper and its 134-horsepower, 1.5-liter three-cylinder, the jump from a 121-horsepower 1.6-liter four-cylinder doesn’t sound like much on paper.

At $20,745 to start, the base Cooper is still the money-saving fuel miser, yet it gains real enthusiast appeal. With 170 pound-feet of torque, 56 more than its anemic predecessor, the Cooper slices nearly two seconds from a 0-to-60 mph run, at 7.3 seconds with a six-speed automatic transmission. And this humble three-cylinder is a social climber: In hopped-up form, it powers the rear wheels of the futuristic $136,000 BMW i8 plug-in hybrid.

The Mini Hardtop motivated by these power plants has grown 4.8 inches longer, on a 1.1-inch longer wheelbase. The axles are wider front and rear. The once-pert hood rises higher, making it more difficult in tight spaces to tell where the front corners end. The hood bulge is partly necessitated by pedestrian and crash standards. But small-car fans needn’t fret, for this Anglophile charmer is still nearly a foot shorter than a Honda Fit or Ford Fiesta.

In the last Mini Hardtop, putting adults in the rear seat was a theoretical exercise. There’s now 2.9 inches of added legroom and 3.1 inches of extra shoulder space. Under the hatch is 8.9 cubic feet of cargo space, a gain of nearly 50 percent. Total storage with the rear seat folded grows by 58 percent, to 38 cubic feet.

Curb weight doesn’t suffer much, with a gain of 60 to 92 pounds. The heaviest Cooper S automatic weighs in at 2,795 pounds, which would have shocked owners of the original, truly miniature Mini of the 1960s, which weighed as little as 1,360 pounds.

The Mini can seem expensive on a square-foot basis. But the all-new design delivers a lot for the money. Standard features include an engine stop-start system, the drive mode selector, keyless locking, push-button start and eight air bags, including two knee bags up front.

But beneath its familiar skin, the new Mini is now a BMW to its core. Good luck finding a Beamer that starts at barely $20,000 — or that, sensibly equipped, stays below $30,000. If you just tell yourself that this British coupe is really a baby BMW, the Mini may come off as a fair deal.