We present a review on our project PRINTOPTICS, looking back on 6 years of successful development of complex 3D-printed microoptical systems fabricated by femtosecond direct laser writing. Specific goal of the project was to realize the full value chain of optical design, simulation and manufacturing with suitable printing materials. Main benefit is a completely new generation of micro-optics, which combines free-form lenses in complex structures on a size of a few 10 to 1,000 μm. During the project we were on the one hand able to improve simulations methods and on the other hand to develop novel optical design concepts for 3D-printed imaging and illumination systems.