Traditionally, to sense particular quantities, sensors are mounted on structures and both are optimised independently. Such optimised sensors generally perform very well. However, giving their characteristics, such as form-factor and measurement range, they may not be the best solution and only allow for limited complexity as assembling and interfacing become increasingly complex with increasing sensor count. Over the last decade the interest in 3D printing of functional structures, rather than rapid prototyping of non-functional structures, has seen a considerable increase; technologies like multi-material 3D printing allow to incorporate electrically conductive materials in dielectric embedding. This opens the route to 3D print electrical connections and sensors _while_ printing entire structures. This has the potential to integrate many sensors and connections and holistically optimise for specific intended applications. For mechanical sensing principles that seem rather suitable for 3D multi-material printing include piezo-resistive and capacitive sensing, although piezo-electric, optic and many others have been shown as well. Next to mechanical sensing also bio-potential, chemical, and magnetic sensors have been demonstrated, alongside 3D printed batteries. In my lab we focus on the development of 3D printing technology for sensing, addressing challenges like print quality, anisotropic conduction, nonlinear mechanical and electrical behaviour, etc. Intended applications are in biopotential measurements and interaction sensing for wearable robotics and medical aids, flow-sensing, beam deflection control, thrust control for UAV applications, etc. In this presentation I will describe developments in these fields as well as multiple examples of our own work.