Corsets were tight garments designed to distort a woman’s figure to conform to fashion trends. The prevailing shape and level of comfort shifted over the decades. Dresses were looser in Medieval times, making corsets unnecessary. Fashion evolved to include a cote or sort of corset that was worn on the outside of a flax shift or other dress.
Catherine de Medici brought Italian-style corsets to France in the 1500s. Napoleon Bonaparte did away with them in the 1800s, leading to the rise of figure-concealing empire-waist dresses in France’s Empire and England’s Regency periods.
In the 1500s corsets in England and Spain were designed to be worn as undergarments. They flattened the abdomen and compressed the bust. Stiffeners were made from steel wrapped in fabric, bone, or wood. The female form was minimized to highlight the elaborate design of gowns. However, necklines could be low-cut to emphasize the curve of the breasts.
Clothing styles changed to emphasize smaller waists and fuller breasts. Corset design followed suit, as corsets were engineered with boning on the sides and laces on the back.
Sources:
http://www.fashionintime.org/history-of-womens-corsets-part-1/
http://sultryladycorsets.com/corsets-in-history/#sthash.jQrzluzM.dpuf
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