A close relationship exists between the advances of cosmic-ray physics and technical developments. Thus the development of highly sensitive ionization chambers, eventually to become self-recording instruments, was an essential prerequisite of the observations which first suggested, then proved the extraterrestrial origin of the radiation. The invention of the Geiger- Müller counter and of the associated coincidence devices opened the door to the investigation of the physical properties of the local radiation. Also "c.r. telescopes," made of G.M. counters, discovered the E-W effect, showing that primary c.r. are positively charged particles. The development of cloud-chambers suitable for c.r. observations, and the development of nuclear emulsions were responsible for the discovery of "new" elementary particles in the local radiation (the positive electron, the µ-meson, the π-meson, the "strange" particles). New techniques involving the use of very large detector arrays produced important advances in the study of air showers showing that the primary spectrum extends beyond 1020 e.v. Finally, the availability of space vehicles, coupled with the development of new suitable detectors made it possible to determine the chemical and isotopic composition of the incident radiation.