What fundamental architectural element of aircraft did the Montgolfiers establish that remains unchanged in modern hot air balloons?

Answer

An envelope to contain the lifting medium and a suspended gondola

The brothers established the basic architecture consisting of an envelope designed to contain the lifting medium and a basket or gondola suspended below it, a principle still used today.

What fundamental architectural element of aircraft did the Montgolfiers establish that remains unchanged in modern hot air balloons?
inventionaviationflightballoonMontgolfier brother