functional elements, chiral photonic crystals, photonic metamaterials and quasicrystals. With this technology becoming commercially available, [ 1 ] many novel ideas have been realized by scientists around the world. Some of these developments can already be seen as new research areas enabled by 3D µ-printing.Many excellent reviews of the underlying technology have recently been published, and we give here just a short selection. [2][3][4][5] With the present progress report we want to summarize the tremendous technological development during the last fi ve years as well as to give an overview over some vastly growing research fi elds enabled by this development. As the number of research papers based on 3D µ-printing as enabling technology is exploding, we intend to categorize the most recent developments to identify future research directions and possible novel fi elds for the years to come. Recent Technological Advances in 3D µ-PrintingFrom the fi rst proof-of-principle in 1997, [ 6 ] the µ-printing community has continuously been expanding the structuring capabilities of µ-printing systems overcoming limitations such as structuring speed, sample volume, complicated pre and post processing, as well as minimum feature size and resolution. Progress is made along two directions: First, extending the aforementioned benchmarks of µ-printing systems. Second, techniques that move µ-printed structures towards functional devices. These two directions obviously are intertwined and require interdisciplinary research efforts on new photocurable materials, complex light-matter interaction, reaction kinetics as well as processes on a molecular level infl uencing structure formation. The most infl uential technological advances are summarized in this section.Section 2.1. covers recent work leading to a tremendous increase of the capabilities of µ-printing systems. Section 2.2. describes superresolution concepts exploiting light-matter interactions to achieve smaller feature sizes and higher structural resolution. Section 2.3. reviews spatial light modulator (SLM) based laser lithography providing additional degrees of freedom by shaping the wavefront of the laser beam. Laser Sources, Scanning Devices, and Writing GeometryThe high complexity of ultrafast fs-lasers drives the community to look for alternative laser sources, leading to cost and In this progress report the development of three-dimensional µ-printing and its impact as an enabling technology onto different scientifi c fi elds is reviewed. Driven by direct laser writing via two-photon absorption, the technology has reached a level of maturity and ease of application such that 3D printing on the micrometer scale can now be considered. While the underlying technology is still developing towards higher resolution and increasing speed of fabrication, the last fi ve years have seen new fi elds rising that were obviously enabled by 3D µ-printing. Among the recent technological developments discussed in this progress report are the fi elds of super-resolution lithography ...

topographies might on the long run guide the design of novel implants with decreased implant failure rates, if osteoblastic functionality is simultaneously secured by the structures.

The influence of three‐dimensional topographies on viability parameters of osteoblast‐like cells is investigated via a systematic variation of structural parameters. On page 6573 J. K. Hohmann and G. von Freymann report which topographies significantly enhance proliferation and how structural parameters influence cell morphology and differentiation. Cover design by Judith K. Hohmann and Christoph Reinheimer.