“…In particular, the Special Issue gathers together 22 papers concerning current research efforts focused on human-computer interaction (HCI) through natural and intuitive modalities including hand/body gestures [ 1 , 2 , 3 , 4 , 5 , 6 ], face recognition [ 7 , 8 ], gaze/eye tracking [ 4 , 9 , 10 ], biosignal analysis [ 11 , 12 , 13 , 14 , 15 ], speech recognition [ 16 ], activity recognition [ 17 , 18 ] and their related issues. Moreover, the Special Issue contains papers related to the architectural design of smart environments [ 19 , 20 ], with a particular focus on the exploitation of sensors for gathering information related to the environment [ 21 , 22 ]. In the following, an overview of the papers included in the Special Issue is provided, by summarizing their main contribution to the state-of-the-art.…”