After some forty years in the academic world and before abandoning a position as an employee of the State educational system to enter the new world of "pensioners", it seemed worthwhile to the first author (J.-P.B.) of this brief discussion to compile a short document that presents a synopsis of the knowledge acquired, taught and put to use for more than four decades. This fascicle reviews only the foraminifers, which, along with calcareous nannofossils, are the fundamental tools of modern biostratigraphy, used for worldwide oceanographic studies and for the correlation of oil wells. It deals essentially with the small foraminifers, that is those of modest size without a complex internal architecture. These include the planktonic foraminifers of which the rapid evolution and great dispersion permit the establishment of reliable biochronologic scales of reference.This short course is intended for students preparing for the CAPES (Certificat d'aptitude au professorat de l'enseignement du second degré = Certificate of Aptitude for a Professorship of Instruction in the Second Grade), for students working toward the Aggregation in Natural Sciences in pursuit of a scientific career in the universities or in the CNRS (Centre National de la Recherche Scientifique = National Centre for Scientific Research), and for students who hope to work in the oil industry where a specialization in the field of micropaleontology is considered useful and is still valued. It will also interest amateur naturalists and that portion of the general public attracted by the beauties of the microscopic world, now living, or extinct and represented only by fossils.