Titan is a massive Saturn moon characterized by the richest atmospheric chemistry of the entire solar system. In particular, organic macromolecules with a high content of nitrogen are formed in the upper atmosphere starting from the main atmospheric components, molecular nitrogen and methane. In our laboratory, we have investigated elementary reactions involving atomic nitrogen in its first electronically excited state and aliphatic or aromatic hydrocarbons present in the atmosphere of Titan. The experimental technique employed is the crossed molecular beam method with mass spectrometric detection. All the experiments have been complemented by dedicated electronic structure calculations of the reactive potential energy surface and statistical estimates of the product branching ratios. We have also investigated the reactions of atomic nitrogen with nitriles like HCCCN or C2H3CN, pyridine, H2, and H2O. The implications for the photochemical modeling of Titan and prebiotic chemistry will be noted.