These days, three times as many crossovers are sold as SUVs and minivans combined. Even SUVs in their Clintonian fin-de-siècle glory days cannot touch the growth of the crossover. Just take in these numbers.

Data: IHS Automotive

Last year, roughly speaking, two crossovers were purchased for every three cars. It's tough to compare apples to apples, but in April, IHS Automotive analyst Tom Libby noted that small crossovers were the single best selling segment of any type of vehicle, including midsize sedans, which are the staple crop of the automotive industry.

"If the trend we have witnessed in the first two months of 2014 continues for the remainder of 2014," Libby wrote, "it would mark the first time in recent memory—if not ever—that a car segment did not lead the industry."

Now halfway through the year, "it seems like that might be case," Libby's colleague Brinley said, though obviously there's still some time left in the year.

In comparison with the rise of Android, say, or WhatsApp, this change may not look impressive. But this is an industry that measures change in decades, that requires new factories to build different kinds of cars, and that has been selling something that someone born in 1890 could understand.

In other words, in the car business, the crossover is what monumental, generational change looks like.

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Crossovers are like SUVs with the rough edges rounded off. The original SUVs like the Ford Explorer were built atop the American car companies' truck platforms—they employed truck construction methods and components. But when Toyota debuted the first crossover, the RAV 4, it was built on a car body.

"A truck frame, you could lift the body off the car and it would still drive. Whereas most crossover utility vehicles are monocoque— single body—if you took the body off, the wheels would fall off," said Michael McHale, Subaru's director of corporate communications. "It affects handling and weight and maneuverability."

So, crossovers look kind of like a small SUV, but they drive like a regular car.

The boxy edges of the SUV are also literally rounded off in most crossovers, as their designers strain to optimize the aerodynamics of the vehicle. But they can't get too streamlined because, as Brinley put it, "the most efficient space is a box." So, most car companies have converged on the compromise design.

"Frankly, if you lined up a Ford Escape, a Honda CRV, and a Toyota RAV4, and you were looking at them 50 yards away and you were an average customer, I don't think you could tell the difference," Toyota's Gregory Lang told me. "Somebody in the industry could, but the crossovers have collapsed on a certain formula that seems to be very in vogue. Some sleekness but a strong dose of utility... Like a lot of things, there's a sweet spot in the middle."