I graduated in 1997 with the first phase coherent optical frequency measurement on atomic hydrogen using. The key instruments at that time have been the optical interval dividers and modulator type optical comb generators. Already during my PhD I tested certain properties of combs generated by mode locked lasers, like recording beat notes with other lasers. Right after graduation I assembled the first selfreferenced optical comb generator based on the 7f-8f technique. Soon after, I could replace this by a much more compact f-2f technique. The long lasting problem of optical frequency measurement was solved and from then on, I devoted myself to improving spectroscopy. The uncertainty of the 1S-2S transition frequency has been reduced right after the introduction of the frequency comb by a factor of 2 and subsequently by a factor 40 through improvements of the spectrometer. To generate more hydrogen data, I designed and supervised a new experiment on the 1S-3S transition using two-photon direct comb spectroscopy. Another activity includes the usage of our 1S-2S apparatus as a source of cold 2S atoms for an improved measurement of the 2S-4P transitions. Meanwhile both experiments contributed significantly to the so-called “proton radius puzzle”, that has been a serious discrepancy between precision spectroscopy and predictions from Quantum Electrodynamics. Another experiment that I have started, aims at high-resolution laser spectroscopy in the extreme ultraviolet on stored hydrogen-like helium ions. I was leading a project that designed and implemented astronomical frequency combs that are now routinely used to detect extrasolar planets at the largest telescopes operated by the European Southern Observatory (ESO).