Pioneers of Microbiology describes the lives of the various actors who took part in the development of bacteriology from the origin to present times. It may be read on several levels, including the history of the science itself and as an introduction to the key pioneers in the field. We will see some names, such as Lancefield, Petri, Escherich or Proskauer, who helped shape the everyday work in laboratories around the world. But, above all, we will trace the birth and development of the great fundamental concepts of our scientific knowledge, such as spontaneous generation, transformism, and antibiosis.