The correspondence between the naturalist Teodoro Monticelli and the diplomat Paolo D’Ambrosio is a representative section of the extensive correspondence belonging to the scientist, now preserved at the Biblioteca Nazionale di Napoli “Vittorio Emanuele III”. Teodoro Monticelli, still considered a pioneer of volcanology, was indeed at the center of a vast and prestigious scientific network, gaining worldwide fame among his contemporaries thanks to his studies on Vesuvian activity. His correspondent, Matteo D’Ambrosio, was a refined intellectual quite experienced in the fields of literature and education, as well as ambassador of the Neapolitan Kingdom in Denmark and Sweden between 1818 and 1821. During the Napoleonic domination (1806-1814), Monticelli played a key role in some of the most important cultural institutions of the Kingdom, such as the University and the Società Reale. They both shared a deep and lasting friendship, probably born in their youth, while they were involved in Jacobin experiences. They had common philanthropic intentions, based on the priority of education and scientific culture as an essential starting point to improve the living conditions of the common people, the economic development of the nation, and the birth of a new, true civil society. The correspondence reproduces the 44 letters, between Teodoro Monticelli and Angelo D’Ambrosio between 1818 and 1827. These documents show how the Kingdom of Naples was far from being isolated and describe a complex system of intellectual exchanges that reached its peak during the Enlightenment and represented for centuries the main means of communication among the educated few throughout Europe.