In the fourth m onth of the twenty-third year of Zhenguan（649），Tang Taizong was overturned by his ninth son，who assumed the throne with a new reign nameofYongwei.TheninthsonthenbecameTang Gaozong.After assuming the throne，Gaozong continued to implement the policies of Taizong so that his reign continued the legacy of the Zhenguan reign.In 655，the sixth year of his reign，Tang Gaozong set up Wu Zetian as empress and Wu Zetian began to oversee governmental affairs.In 683，Gaozong died of illness.In the ninth month of 690，the sixty-seven-year-old Wu Zetian changed the reign name of the dynasty to Zhou and began to rule as emperor herself，in her own name.She became the only female emperor to formally be declared as and rule as empress in China.Although she had usurped power，and was later denounced for consolidating power in her own hands，nonetheless the political and economic situation of the Tang Dynasty continued to move forward during her reign.She had a book published on agricultural practices and greatly developed agricultural production.She created the conditions for a substantial improvement in the material wealth of Tang-dynasty lives.However，during the latter part of her reign she doted on oneminister and became very dissatisfied with her premier.In 705，the Premier Zhang Jianzhi and others mobilized a palace coup that forced her off the throne.The previous Tang-dynasty reign name was restored.In a final struggle for imperial power，Li Longji defeated the Empress Wei group and assumed the throne.He changed his reign name to Kaiyuan，and became Tang Xuanzong（reigned712–756）.Xuanzong was a very enlightened ruler，as successor to Li Shimin.He made adjustments in political power，reformed the administrative and military systems，encouraged economic development，reformed the tax system，he revised the waterworks，and generally brought the people to a status they had never before enjoyed.The poet Du Fu has written admiringly of the“flourishing time of Kaiyuan.”
From the time the Tang Dynasty was established up to the years of Kaiyuan，a number of enlightened rulers，includingLi Shimin and Wu Zetian，administered thecountry.Intermsofforeign relations，the Tang Dynasty continued the practice of the Sui and gradually run its administration by three ministries called Zhongshu，Menxia，and Shangshu，all of which strengthened the power of the emperor’s rule.At the same time，Tang re formedtheexamsystemoftheSuidynasty，makingitintoanimportant method and shortcut to finding excellent off icials.Inaddition，tostrengthenrelations with miniority peoples onthe border，Li Shimin adopted a“hard and soft”approach.In 641，or the 15th year of Zhenguan，hemarriedPrincessWenchengto Songtsen Gampo，which pulled Tibet into a tighter liaison with the Great Tang.The renowned“SilkRoad”alsobecame a nimportant conduit at the time for the Central Plains to develop towards the outside，to improve relations with foreigners，to increase economic and cultural exchange.
With few internal or external worries，Tang Dynasty was able to expand and advance in an unprecedented way.The humanities and arts of the early Tang period developed briskly.Poetry，calligraphy，and painting saw the appearance of a number of famous artists.Those poets included“the four outstandings of early Tang，”Wang Wei（699–759），Cen Shen（715–770），and the two greatest poets Li Bai（701–762）and Du Fu（712–770）.In addition to these were the great masters of painting，Wu Daozi and Li Sixun，the calligraphers Yan Zhenqing and Liu Gongquan，and the musician Li Guinian.All were representative of Tang-dynasty cultural talent.
Tang sancai（tri-colored glazed pottery）is one of the marvels of handicrafts of the Tang era，which competes in technical excellence with our arts today.
Tang sancai is the term applied to a kind of ceramic that is glazed with different colors and that was used in both daily life and as an article in funerary practices to accompany the deceased.The colors include green，blue，yellow，white，red，and orange，but the primary colors are yellow，green and orange，so it is called sancai or tri-colored.Many types of objects were made with this form of ceramic，including human and animal figurines and various shapes of pots.The primary production places of sancai were Luoyang and Chang’an，also some parts of Henan and Shaanxi.In the process of making the ceramic，the glaze was allowed to run down naturally，so that the results were often strange and wonderful and no two were ever exactly the same.The artistic creation of Tang sancai reflected the special nature of the age and of society at the time.The warrior figures are fierce and robust，the horses are magnificent steeds，and the camels are vigorous.All are well endowed with the vigor and strength of early Tang.From the plumpness of the faces of ladies，one can see also that this was a period when plumpness was considered a mark of beauty.