3D sensors are a promising option for the innermost pixel layers at the High Luminosity LHC. However, the required very high hit-rate capabilities, increased pixel granularity, extreme radiation hardness, and reduced material budget call for a device downscale as compared to existing 3D sensors, involving smaller pitch (e.g., 50×50 or 25×100 μm2), shorter inter-electrode spacing (~30 μm), narrower electrodes (~5 μm), and reduced active thickness (~100 μm). The development of a new generation of 3D pixel sensors with these challenging features is under way by many research groups, in collaboration with processing facilities like FBK, CNM, and SINTEF. This paper talk will review the lessons learned from existing 3D detectors, and will address the main design and technological issues for small pitch 3D devices. Preliminary results from the electrical and functional characterization of the first prototypes will be reported and compared to TCAD simulations.