Featured on National Geographic’s Instagram account with 6.5 million followers on January 15, this photo shows people standing on top of Ta Xua, the 10th highest peak in Vietnam at 2,865 meters and situated between Yen Bai and Son La provinces.

By late November the temperatures here fall to 14-19 degrees Celsius during day and 9-10 degrees at night.

The best time to see clouds there is between December and March.

"In the early mornings from October to April a sea of clouds appears in this mountainous region, creating a magical beauty," Viet said.

Featured by NatGeo's photo editors on January 19, this photo captures the beauty of tea hills shrouded in thick fog in Long Coc Commune in Phu Tho Province, around 112 kilometers from Hanoi.

Long Coc has in recent years become a popular destination for photographers thanks to tea hills that resemble upturned bowls placed next to each other.

Tea farming is one of the main sources of income in Phu Tho, a place sacred for Vietnamese as the birthplace of the nation's mythical founders, the Hung Kings.

This photo in NatGeo in January shows a tourist standing inside Son Doong, the world’s largest cave, as the sun shines down.

"To take this photo, I woke up at 5 a.m., went through the usual trekking route that usually takes around 1.5 days in some four hours and waited for the first rays of sunlight to penetrate deep into the cave," Viet said.

A four-day-three-night expedition of Son Doong Cave costs VND69.8 million (around US$3,000) but numbers are strictly limited every year.

During the expedition, tourists can explore the cave together with an expert, see unique underground rainforests and scale the 90-meter "Great Wall of Vietnam" at the end of the cave with ropes and ladders.

They get three freshly cooked meals every day and sleep in some of the world's greatest campsites.

This photo, featured in May, shows a farmer cycling by a lone tree on the outskirts of Hanoi.

Viet, who started his photography career in 2007, has won a number of top prizes in prestigious photo contests and is the only Vietnamese photographer to collaborate with National Geographic.

A street vendor walks on Hanoi’s Ceramic Road. The murals on the Red River dike are made from ceramic tesserae from Bat Trang village, famed for its centuries-old traditional pottery. The photo was published on NatGeo in July.

Featured in August, this photo captures an aerial view of Ma Pi Leng, one of the most dangerous passes in Vietnam’s northern highlands.

Soaring above the pass is a mountain 2,000 meters high along whose side is the Hanh Phuc (Happiness) Road connecting Ha Giang Town, Dong Van District and Meo Vac District in Ha Giang Province, around 300 kilometers (186 miles) from Hanoi and close to the China border.

Below the pass is the Nho Que River with its turquoise waters, popular for kayaking and boat tours.

The shot, chosen by NatGeo editors in August, shows young men lifting a teammate who hugs a wooden ball at a ball wrestling festival in Van village in the northern province of Bac Giang's Viet Yen District.

Held from the 12th to the 14th of the fourth lunar month every four years, the festival features ancient rituals and spiritual beliefs of a wet rice civilization, with local farmers praying for bumper crops and good weather for the rice season.

In 2018 NatGeo magazine listed the festival as one of the world's most extraordinary traditions.

This photo featured on NatGeo in October has a fisherman rowing his coracle to harvest seaweed called sargassum, which usually thrives in coral reefs and underwater rocks and emerges from the water surface once fully grown, during the dry season between May and July.

Viet took the photo in Hon Kho Islet during his trip to beach resort town Quy Nhon in central Vietnam.

The seaweed is used as medicine for goiter and as fertilizer.

The photo featured in December captures a flock of seagulls flying around two whales just off Vung Boi-De Gi beach near Quy Nhon. The beach is famous for its clear, blue waters. "Mother and daughter Bryde's whales on the coast of De Gi in Binh Dinh Province," Viet wrote in his caption.