The telecommunications industry was one of the first users of micro-optics, back in the 1980s. The integration of semiconductor lasers, micro-optics and fibers into small packages was the economic basis of efficient optical networks. Today micro-optics are a marketable commodity and are well-established key components in many industrial areas with higher-than-average growth rates. Based on their experience with microelectronics, several institutes and companies developed technologies to produce small lenses with photolithography, etching and melting of glass or photoresist. On one hand, they produced reproducible structures with diameters down to a few microns; on the other hand, the limited optical quality restricted the number of applications. Ongoing development of high-resolution micromachining tools opened new possibilities to produce well-defined optical surfaces for lenses, prisms and mirrors. Furthermore, micro-optics were produced not only as individual lenses, but also in arrays -- an important new feature in optics and an exciting tool for optical designers.