Underneath the fabric, a modern bra is a small piece of structural engineering — usually more than 20 individual pieces stitched together to do one job: support weight without anyone noticing the effort.
Runs over the shoulder to stabilize the cup and carry a small share of the load — typically around 20% of total support, less than most people assume.
The small hardware that lets a strap lengthen or shorten, adjusting fit without altering the garment itself. A 1920s-era innovation that's barely changed since.
Holds and shapes the bust. Modern cups are usually built from two or three molded or sewn panels rather than a single piece of fabric, for a smoother, rounder profile.
The fullest point of the cup. A well-fitted bra positions the apex to point forward — the classic marker of "inward and upward" fit that fitters check for.
A curved band — plastic or metal — sewn along the base of the cup to lift and separate. Introduced commercially in the 1930s, though early patents date to the 1890s. Optional: plenty of styles skip it entirely.
The panel of fabric bridging the two cups at the center front. A short gore sits flat against the sternum; taller gores appear on fuller-support or plunge styles.
The horizontal base encircling the ribcage. It does the majority of the structural work — often cited at around 70–80% of total support — which is why a snug, level band matters more to fit than cup size alone.
The hook-and-eye (or occasionally front-clasp) fastening at the back or front. Multiple columns of hooks allow the band to be taken in as elastic relaxes with wear.
Close-up photography shows how these pieces come together — lace overlay, cup seaming, and band elastic worked into a single finished product.
Lace overlay stitched onto a structured cup, showing the seam lines that give a molded cup its shape.
A contemporary full-cup style — the descendant of nearly every part diagrammed above, largely unchanged in principle since the 1930s.