We envision methods and systems that permit low-cost, unobtrusive quantification of human motion in 3D and the semantic interpretation of human activities, based on markerless visual input. Such methods and systems will unlock tremendous opportunities in application domains that are limited only by human imagination. Existing methods for human motion capture and interpretation are usually invasive and rely on expensive hardware that is deployable in laboratory environments. We aim at developing methods for accurate and markerless human motion capture and interpretation with affordable, commonly available cameras. To do so, we will rely on our award-winning, pioneering work on model-based approaches to human motion capture and interpretation and we will combine it with machine learning approaches. We advocate that hybrid methods that fuse generative, model-based approaches with discriminative, deep learning ones, is the key innovative methodological element that will enable us reach our ambitious goals. We will consider methods for estimating the pose of head/facial landmarks, of hands and of the human body as well as for facial expression recognition, gestures recognition and action understanding. To showcase their application potential, we will exploit the developed methods in vision-guided AR/VR and in assistive healthcare applications. We also propose the purchasing of a marker-based motion capture (MOCAP) system and associated computing infrastructure. The importance of this to I.C.HUMANS research is imperative because it can provide groundtruth- annotated training data for the machine learning components of our methodologies and for the quantitative evaluation of the developed solutions. The requested infrastructure will also become accessible to other research laboratories and industries in Greece that are interested in motion capture, possibly from different perspectives (robotics, ergonomy, biomechanics, etc). To guarantee the maximization of the benefits of the infrastructure for Greece, I.C.HUMANS will deliver a concrete use plan of the MOCAP system and its associated computing infrastructure.