The first member of the Section of Natural Sciences, one of the three Sections of the Romanian Academic Societies established in 1867, was chosen in 1870. This was Petrache Poenaru, a truly remarkable person who had a genuine Renaissance spirit and was a pioneer in Romanian science and culture in many domains. Poenaru, who had studied in Paris and Vienna and, later, completed his specialized studies in England, was a mathematician, physicist, engineer, inventor, teacher and organizer of the educational system, as well as a politician, agronomist, and zootechnologist, founder of the Philharmonic Society, the Botanical Gardens and the National Museum of Antiquities in Bucharest.

Also amongst the pioneers was the physicist Emanoil Bacaloglu, the first Vice President of the Scientific Section and then, in 1879, Poenaru’s successor as President of the Section of Natural Sciences.

He was the author of the first university textbooks in mathematics and physics, through which he normalized scientific terminologies and nomenclatures in the Romanian language. To stay within the realm of physics, we must mention the most illustrious physicists who were members of the Romanian Academy. Dragomir Hurmuzescu invented a sensitive electroscope which was afterwards used by the discoverers of radioactivity, and was one of the founders of Romanian radio broadcasting. Stefan Procopiu, Professor of Physics at the University of Iasi, made the theoretical discovery (independently of Niels Bohr) of the magneton, that is, the quantum of magnetism associated to the electron.

He also discovered a phenomenon of induction, known as the "Procopiu effect", which many years afterwards would be used in the United States for the memory devices of computers. Alexandru Proca published the fundamental equations of elementary particles, which Louis de Broglie named "Proca’s equations".

Closer to our own age, the "golden generation" of physicists included Badarau, Hulubei, Titeica, Ciorascu and Agârbiceanu, all remarkable personalities in the Academy’s Institutes of Physics and Atomic Physics. The Institute of Physics was established and originally directed by Eugen Badarau, a specialist in plasma physics and electrical discharges in gases. The Institute of Atomic Physics was the creation of Horia Hulubei, who had earned his doctorate in Paris under the tutelage of Professor Jean Perrin, and then worked in M. & Mme. Curie’s laboratory. Hulubei made important contributions in the fields of radioactivity, X-ray spectroscopy and nuclear physics. Serban Titeica was the founder of the Romanian school of theoretical physics and made valuable contributions in statistical physics and quantum mechanics. Florin Ciorascu, one of the directors of the Institute of Atomic Physics, published works on electronics, physics and nuclear engineering. Ion Agârbiceanu was the creator of the first laser in Romania, and was highly regarded in the field of optics.

In the realm of chemistry, the first name which must be mentioned is that of Petru Poni, a professor at the University of Iasi and two-time President of the Academy. He initiated the first explorations into the mineral and petroleum wealth of Romania and his high-school chemistry textbooks were in use for over 50 years. Constantin Istrati, a chemist and physician specialized in organic chemistry and balneology, was Vice President and President of the Romanian Academy. He did for Bucharest what Poni did for Iasi in terms of organization and pedagogy, as teacher and minister of education. Nicolae Teclu, who taught and worked in Vienna, is renowned for the invention of a high-performance gas burner known as the "Teclu burner", still in use today. Gheorghe Spacu, the best-known Romanian inorganic chemist, founded new schools of research in the domains of complex combinations as well as discovered new methods for the analytic determination of many metals. His son, Petre Spacu, continued his father’s tradition both as Professor at the Bucharest Polytechnic Institute and as a researcher, primarily in the field of coordinative chemistry. The creator of the Romanian school of physical chemistry was Ilie Murgulescu, Vice President and President of the Romanian Academy and founder of the Academy’s Institute of Physical Chemistry, which now bears his name. His principal original contributions were in relation to the thermodynamic properties of melted salts, and he authored a monumental six-volume treatise on physical chemistry. Also among the most distinguished Romanian chemists is Costin Nenitescu, the originator of a school of research in organic chemistry and of the Academy’s Center for Organic Chemistry, which currently bears his name. His principal discoveries include three new reactions and a hydrocarbon, which was likewise named after him.

The geonomical sciences, which comprise geology, geophysics, geography and pedology (soil science), have been represented in the Section of Natural Sciences since 1871. Among its pioneers was Grigore Cobalcescu, one of the first Romanian geologists and paleontologists and the author of important studies regarding the Eastern Carpathian Mountains and that region’s petroleum deposits. Sabba Stefanescu primarily studied tertiary formations and paleontology. His son, Stefan S. Stefanescu, was a valuable geophysicist, whose activities were intently focused on geophysical prospecting through the use of electromagnetic methods. Gheorghe Munteanu-Murgoci was a geographer, geologist and pedologist, who made important contributions in the fields of mineralogy, speleology and tectonics. He studied the natural resources of Romania, especially salt, petroleum and mineral water deposits. Ion Simionescu was an eminent geologist, geographer and paleontologist who served as Vice President and President of the Academy, and who was the author of several monumental works about Moldavia at first, then about the entire Romanian territory. The popularization of sciences and the development of a scientific culture among the general public were chief among his preoccupations. Simion Mehedinti is generally considered to have been the founder of Romanian geography; he studied the specific object of geography, its place among the other sciences, and its laws and methods, thus becoming the creator of a veritable philosophy of geography. He was the author of important works in the areas of human and economic geography and ethnographic geography.

In the sciences of agriculture and forestry, Ion Ionescu de la Brad must be the first to mention, as founder of modern Romanian agriculture. He combined research with social practice, establishing model farms and participating in the accomplishment of the agricultural reform of 1864. Gheorghe Ionescu Sisesti founded the Institute for Agronomical Research and created new breeds of cereals with increased fertility.

Among the foreign Honorary Members, we will only mention those personalities who are still alive: the chemists and Nobel Prize laureates Jean-Marie Pierre Lehn and Ilya Prigogine, and the physicist Alexandr Prohorov. From among the ranks of scholars of Romanian origin currently living abroad, the following scientists are Honorary Members of the Academy: physicists Radu Balescu (Belgium), Gabriel Dan Cacuci and George Comsa (Germany), and chemists Gheorghe Mateescu and Virgil Percec (United States) and Alexandre Revcolevschi (France).

At the present, the natural and exact sciences are grouped into four specialized sections of the Romanian Academy, these being the Section of Physical Sciences, the Section of Chemical Sciences, the Section of Geonomical Sciencesand the Section of Agricultural and Sylvicultural Sciences. Nine institutes and research centers function under the direction of these sections: 

• the Center for Advanced Studies in Physics in Bucharest, the most recently founded unit of the Romanian Academy, established in 1999;

• the Center for Organic Chemistry Costin Nenitescu in Bucharest, involved mostly in the fields of heterocyclic compounds, theoretical organic chemistry and nuclear magnetic resonance; 

• the Institute of Physical Chemistry Ilie Murgulescu in Bucharest, principally concerned with modern methods and instruments in physical chemistry (catalysis, electrochemistry, corrosion, etc.); 

• the Institute of Macromolecular Chemistry Petru Poni in Iasi, which is mainly involved with research into high-performance polymers and their laws, processes and prospective materials; 

• the Institute of Chemistry in Timisoara, principally concerned with colorants and elementary organic compounds, especially those which are biologically active; 

• the Laboratory of Inorganic Chemistry in Timisoara, dedicated mostly to research into inorganic compounds with special properties; 

• the Institute of Geodynamics Sabba S. Stefanescu in Bucharest, which studies active geodynamic systems, in particular the Vrancea seismogenic zone, and coordinates a network of seismological and geophysical instruments; 

• the Institute of Geography in Bucharest, which has produced important maps and atlases of Romania and conducts research into natural and man-made geographic modifications; 

• the Center for Oenological Research in Iasi, dedicated to the study of Romanian vineyards and wines, with an emphasis on the methods of preservation and protection of their specific characteristics.

Among the most prestigious periodicals of the four Academy sections of natural and exact sciences, we will mention: Romanian Journal of Physics, Romanian Reports in Physics, Revue Roumaine de chimie, Romanian Chemical Quarterly Review, Cellulose Chemistry and Technology, Revue roumaine de géophysique, and Revue roumaine de géographie, all of which are published by the Romanian Academy Publishing House.