The evolution of the deep robe (深衣) went through two processes: first, the adoption of the "curved hem" by lingerie brands. Before the appearance of the deep robe, people's clothing was divided into two parts - the top and the bottom. The top (blouse), bottom (skirt), and inner pants each had their own functions, with no connection between the blouse's hem and the skirt's hem (lower edge). Later, as the deep robe removed the apron, it became difficult to handle the lower part: if slits were made on both sides of the hem, there would be a risk of exposing too much; if no slits were made, it would affect walking. To resolve this contradiction, the ancients came up with the method of the "curved hem," which involved extending the blouse's hem to form a triangle. When worn, it was wrapped around the back and tied with a belt, resembling a swallow's tail from behind. This way, it was convenient for walking and avoided exposure. As underwear became more perfected, it further developed into the "straight hem." Compared to traditional tops and skirts, this deep robe was much simpler to wear and more fitting to the body. Therefore, during the pre-Qin period, it was used as casual wear by feudal lords, high-ranking officials, and scholars, and also as formal attire by commoners.
The dark red silk printed and dyed straight-hemmed deep robe with wide续衽was unearthed from Tomb No. 1 at Mawangdui in Changsha. It is 130 cm long, with a total sleeve length of 236 cm, a sleeve width of 41 cm, a cuff width of 30 cm, a waist width of 48 cm, a hem width of 57 cm, a collar width of 29 cm, and a hem edge width of 38 cm. Its style features a crossed collar, right lapel, wide sleeves, and straight hem, with wide edges embroidered on both the sleeves and the hem. A major feature of this garment is its wide续衽, which refers to the lapel (anciently called "衽") being attached under the armpit to the lower hem, extending straight down to align with the hem, appearing as a continuation of the right lapel, hence named "续衽". This wide-edged straight-hemmed deep robe was a popular style in the Changsha region of Western Han Dynasty but retained the previous straight hem form, which was adapted to fit the previously mentioned "curved hem" form. It could wrap the wide lapel around the back and secure it with a waistband, providing warmth during winter.