The Unibody Car

Wiki Tells us that

Unibody, or unitary construction, is a related construction technique for automobiles in which the body is integrated into a single unit with the chassis rather than having a separate body-on-frame. The welded “Unit Body” is the predominant automobile construction technology today.

Lancia Lambada were the first company to us the unibody technique or the monocoque technique in 1923, and both Crystler and Citroen were mass producing monocoque vehicles in 1934

with the innovative Chrysler Airflow and the Traction Avant, respectively, and General Motors followed with the Opel Olympia in 1935.

According to Wiki

Spot welded unibody construction is now the dominant technique in automobiles, though some vehicles (particularly trucks) still use the older body-on-frame technique.

The technique has advanced somewhat and instead of the all welded steel with sturdy bridge-like girders that arched front to back,

it is now common to see true monocoque frames, where the structural members around the window and door frames are built by folding the skin material several times.

for example

the Infiniti M
This Blogger tells us that it has an

Advanced unibody construction with a high level of torsional rigidity

Must admit - though - with all its attributes and technical advances I still prefer this

Lancia Lambada