This book complements the two previous volumes with historical portraits - "Great Chemists: The Old Guard" and "Great Chemists: The Golden Age" - which refer to the most important chemists from the time of Lavoisier to the late 19th century.

With the Pioneers, the vast majority of prominent chemists, in the broadest sense of the word, is now covered, since the title of chemist could be claimed by technologists, alchemists, physicians, pharmacists, and amateur "chemical philosophers" in an early stage.

After a brief presentation in the first chapter of the major alchemists, from the Alexandrian times to the 13th century, special emphasis is placed on the pioneer Paracelsus - an alchemist and physician with significant influence on later figures. We then move to "iatrochemistry" and "chemistry," an intermediate period covering two centuries (16th-17th) and characterized as a transitional state from alchemy to chemistry.

Finally, we arrive at the forerunners, contemporaries, and some successors of Lavoisier, who systematically nurtured chemistry as an emerging science. Thus, three centuries (16th-18th) and two cultural periods (Renaissance and Enlightenment) are primarily covered - a period during which the foundations for the development of modern chemistry were laid.

Gradually, the alchemical conception of matter and its metaphysical implications are overcome, and rationalism prevails. In relation to the "nobler" sciences of mathematics, astronomy, and physics, chemistry begins to take its place as a true physical science, albeit with considerable delay.

Thus, it becomes established in the consciousness of other scientists, as well as in society at large, as the science of the transformations of matter that may not turn lead into gold but achieves remarkable performance while interpreting the behavior of substances. Additionally, the contribution of chemistry to the prosperity of peoples begins to become evident.

Many names from the chemists presented are not widely known, and it is sad that even in reputable history books of chemistry, few to none are mentioned for some of them. The progress of any science - and chemistry in particular - has relied on few select individuals, pioneers who had to struggle against very adverse conditions facing three major obstacles: the difficulties of subjugating matter, the restrictions of religion, and the skepticism of their contemporaries who remained attached to outdated ideas.

I believe that I am correcting some historical injustice by shedding light on great individuals and their achievements, along with some references that illuminate their time. Therefore, such an acquaintance is worthwhile, which cannot be achieved otherwise than by resorting to monographs that refer to specific scientists - and that cover only a few of the approximately 30 discussed in this volume.

The bibliography includes only books on the history of Chemistry and not articles or websites from the Internet, which provides abundant material, even complete articles or entire books. More information is difficult to obtain unless one resorts to original sources, to libraries that hold old biographies or first-published works, often in the form of books rather than articles.

I want to believe that I have satisfactorily covered the main parameters of the personalities I present.