2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/134457It is shown that Extensive Air Shower (EAS) longitudinal development has a critical point where an equilibrium between the main hadronic component and the secondary electromagnetic one exhibits a brake. This results in a change of slope in quasi-power law function $N_{e}(Eo)$. The latter leads to a knee in the EAS size spectrum at primary energy of about 100 TeV/nucleon. Many ``strange'' experimental results can be successfully explained in the frames of current approach.Talk given at 30th ICRC, Merida, Mexico (2007) 5 pages, 3 figuresAstrophysicstext