It's quite hard to imagine a time when nightwear did not exist - but the interesting fact specific nightwear is actually a recent innovation.

Here is quick run-down of the different types of nightwear throughout the ages;

Chemises

Chemises were a unisex garment in terms of wearers, and people used them as a sort of early underwear as they became more popular around the Middle Ages. It protected bed clothing from sweat, body oils and dead skin. Over time the chemise became the only piece of clothing to be washed regularly and it was only worn in the bed.

Negligees

Negligees originate from 17^th Century France and, at the time the new garment was highly functional and was generally quite long and made from a reasonably heavy fabric. Over the next three hundred years the negligee changed to match styles of dress and by the early 20^th Century they were shorter lighter and were significantly racier than the original negligees.

Picture shows: Cotton Nightie (Kaftan Style)

Nightgowns/Cotton Nighties

These were developed in the early 1800's and were natural successors of the earlier developed chemises. These nightgowns varied significantly in design, however in general they were made from cotton or flannel and heavier and more practical than negligees.See some here.

Pajamas

Pajamas or PJ's origins can be found in South and West Asia and was brought back by British missionaries as the nightwear of choice for men and boys. In the early 1900's PJs replaced nightshirts and nightgowns for men - they did not really come in to fashion for women until the 1980's where they are now widely available.

Today people wear anything as nightwear - lingerie and other underwear is often used as nightwear along side cotton nighties, chemises and pajamas.