The Asymptotic Giant Branch phase of low and intermediate mass stars (1.2 < M/M⊙ < 6.0) synthesizes nearly half of the heavy elements (A > 56) in the Universe. This evolutionary phase represents an ideal laboratory to test our knowledge of stellar microphysics and macrophysics. In fact, the nucleosynthesis occurring in AGB stars sensibly depends on the adopted physical inputs and on the assumptions in the treatment of physical phenomena like convection, mass loss and rotation. In this contribution we illustrate the characteristics of low mass (1.5 < M/M⊙ < 3.0) AGB models at different metallicities (− 2.2 < [Fe/H] < 0.2). In particular, we highlight the effects induced by the use of proper C-enhanced low temperature opacities and the importance of the treatment of the envelope radiative/convective interface on the formation of the 13C-pocket (the main neutron source). We briefly describe main characteristics of the FRUITY database on AGB stars nucleosynthesis, created by directly coupling a full nuclear network with evolutionary models. Finally, we discuss the effects that the inclusion of rotation has on the s-process pattern in low-mass AGB stars.