One family: Camellia Sinensis

All teas plants are from the family of Camellia Sinensis.

Two main subdivision

Assam: a tall tree with large leaves

Chinese: a shorter tree with small leaves.

It is thought that tea trees are originally from Southeast Asia, with the first tea production in the southern part of China’s current Yunnan province.

Over 6,000 years ago

Since 1978, several archeology research projects led to discovering roots of the Camellia Sinenses plant and pottery in the Tianluo mountains that were estimated to be 7,000 years old. Tianluo Mountain is a part of an archaeological site for the neolithic Hemudu culture, which flourished between 7000 BC and 6000 BC. Confirming

This confirmed it must have been the Hemudu culture, flourishing in 7,000 BC and 6000 BC, that started cultivating and brewing tea.

Shen Nong and the beginning of tea drinking

Chinese classical legend of Shennong, (神農, "God Farmer"), said to have lived some 4,000 years ago; founder of agriculture and forestry as well as basic Chinese Medicine.

In one popular Chinese legend, Shennong was drinking a bowl of just-boiled water due to a decree that his subjects must boil water before drinking it sometime around 2737 BC when a few leaves were blown from a nearby tree into his water, changing the color; the emperor took a sip of the brew and was pleasantly surprised by its flavor and restorative properties.

 https://en.wikipedia.org/wiki/History_of_tea#Geographic_origins

 

Tea in Japan

The first reference to tea in Japan appears in records of the Nara period (710–794),  a period when Japan sent diplomatic missions to Chang'an, the capital of China's Tang dynasty (618–907).

In 804, the Buddhist monks Kūkai and Saichō arrived in China to study religion as part of a government-sponsored mission during the Heian period (794–1185). The Shōryōshū (814) mentions that Kūkai drank tea during his time in China. He returned to Japan in the year 806.

Kūkai is also the first to use the term chanoyu (茶の湯), which later came to refer specifically to the Japanese tea ceremony. Upon their return to Japan, Kūkai and Saichō founded the Shingon and Tendai schools of Buddhism, respectively. One or both of them are thought to have brought back the first tea seeds to Japan during this trip. Saichō, who returned in 805, is often credited for being the first to plant tea seeds in Japan, although the documentary evidence is uncertain.

Eisai and the popularization of tea

The Zen monk Eisai (1141–1215), founder of the Rinzai school of Buddhism, is generally credited for popularizing tea in Japan.

In 1191, Eisai returned from a trip to China and brought back tea seeds which he planted on the island of Hirado, and in the mountains of Kyushu.

He also gave some seeds to the monk Myōe, abbot of the Kōzan-ji temple in Kyoto. Myōe planted these seeds in Toganoo (栂尾) and Uji, which became the sites of the first large scale cultivation of tea in Japan.

At first, Toganoo tea was seen as the finest in Japan, and was called "real tea" (本茶 honcha), as opposed to "non-tea" (非茶 hicha) produced elsewhere in Japan. By the 15th century, however, Uji tea surpassed that of Toganoo, and the terms honcha and hicha came to refer to Uji tea and non-Uji tea.

Sencha
By the 14th century, the practice of drinking powdered brick tea had fallen out of fashion in China. Instead, most tea was hand-fired over a dry wok to stop the process of oxidation, and purchased as loose leaves rather than compressed bricks.

The method of steeping loose tea leaves in hot water came to be known as "boiled tea" (煎茶 sencha), and it soon led to a new way of producing green tea that would work well with this technique. In 1737, an Uji-based tea grower named Nagatani Sōen developed what is now the standard process for making leaf teas in Japan: tea leaves are first steamed, then rolled into narrow needles and dried in an oven.

Sencha grew in popularity over time, and is now the most popular form of tea in Japan, representing 80 percent of all tea produced each year.

 https://en.wikipedia.org/wiki/History_of_tea_in_Japan