Abstract: In the early years of proteomics, mass spectrometry served only as a technique in protein chemistry facilitating the characterization of purified proteins and mapping their posttranslational modifications (PTMs). A bit later this technique almost completely replaced Edman degradation and amino acid analysis. The continuous development of the mass spectrometry techniques created a huge analytical potential allowing the study of nearly complete proteomes in single experiments. This evolution distanced proteomics from protein chemistry and placed it in a novel position. Its capability to identify and quantify in parallel thousands of proteins and their modifications at minute sample amount requirements is one of the most fascinating technological advances in biology today.