In recent years the interest in few-body physics has received a significant boost thanks to experimental investigations of Efimov physics using cold atoms. With the term Efimov physics it is customary to design all the ensemble of universal relations found in few-body systems when the scattering length of the two-body subsystem is unnaturally large (for recent reviews see [1] and [2]).

After a general introduction to the Efimov physics, I will present my work in the study of the Efimov physics for systems up to six particles [3,4]. In order to keep contact with reality, we have worked with a bosonic system made of $^4$He atoms, whose interaction is such that the few-body systems fall inside the Efimov physics. I will show how the universality manifest itself in these systems, and how can be used to relate systems whose natural length differs by several order of magnitude.

[1]. C.H. Green, Phys. Today 63, 40 (2010)

[2]. F. Ferlaino and R. Grimm, Physics 3, 9 (2010).

[3]. M. Gattobigio, A. Kievsky, and M. Viviani, Phys. Rev. A, 86,042513012)

[4]. A. Kievsky, and M. Gattobigio, arXiv:1212.3457 [cond-mat.quant-gas]