After the birth of Nikolai Nikitich (1773-1828), he was immediately recorded as a corporal in the Preobrazhensky Regiment, as was customary in Russian nobility. At sixteen, he served as a flag adjutant to General Field Marshal G.A. Potemkin. Later, he was appointed chamber junker, and under Paul I, he became a member of the Chamber Collegium with the rank of secret advisor and hofmarshal.

Nikolai Nikitich was passionate about social life and showed little interest in managing his factories, which were controlled by A.V. Krapovitsky and N.D. Durnovo. Due to debts and poor management, the factories were on the brink of collapse. Nikolai's sisters, Maria and Ekaterina, needed dowries, which required money. Selling estates and mortgaging factories did not solve the problems. Nikolai found a way out by marrying Elizaveta Alexandrovna Stroganova, the daughter of Baron Stroganov. This marriage brought him part of the Stroganov fortune and access to high society. Elizaveta came from the famous Zagryazhsky family, and her uncle, Count Stroganov, was an influential statesman.

Initially, the couple lived in Moscow and St. Petersburg, but soon Nikolai retired and in 1800 went to Europe. There, he studied new technologies in metallurgy and implemented them in his factories, sending serfs to study abroad. To expand iron trade, he established connections with England and purchased a ship in Italy. In Taganrog, he created a fleet for transporting goods between fortresses.

In Nizhny Tagil, Nikolai built a school, a hospital, an orphanage, and transformed the mining school into the Vyyskoe School. In 1806, he founded an art school, from which the best students went to study in Moscow, St. Petersburg, and even Italy.

The family life of the Demidovs was short-lived. After the birth of their son Pavel, Elizaveta moved to Paris. In 1808, Nikolai also settled there, but soon returned to Russia due to deteriorating relations with France. He created the 'Demidov' regiment and participated in the Battle of Borodino along with his son Pavel.

Nikolai Nikitich was actively involved in charity. He restored the collections of Moscow University after a fire, built bridges and a frigate, gifted a palace to Moscow, and provided funds for a labor house, as well as contributed significant sums to charitable foundations.

In 1813, the Demidovs had a son, Anatoly. After the war, Nikolai went to Paris and then to Italy due to health reasons. He lived in Rome, Pisa, and Florence, where he purchased the San Donato estate and began building a villa.

Nikolai was a passionate art collector. His collection included sculptures, decorative items, and paintings. He commissioned works from renowned masters such as Adamo Tadolini and Pierre-Philippe Thomire. After his death, the collection was transported to Russia, but its whereabouts are unknown.

In Florence, Nikolai continued his charitable activities, building schools and hospitals. His generosity was commemorated with a monument in the square named after him. Nikolai also participated in the colonization of southern Russia, developing vineyards and orchards on his lands in the Kherson province.