Multiplicity fluctuations in high energy hadronic and nuclear collisions

The showers of cosmic rays entering the Earth's atmosphere are main sources of information on cosmic rays and are also believed to provide information on elementary interactions at energies not accessible to accelerators. In this context we would like first to remind the role of inelasticity K and elementary cross section $\sigma$ and then argue that similar in importance are fluctuations of different observables. The later will be illustrated by multiplicity fluctuations in hadronic and nuclear collisions.