With the recent advances in robotics, bioinformatics and nanotechnology, it is now possible today for the biologists to observe and analyze several hundreds or thousands of biological molecules at the same time. This is the case at the DNA level, in genomics, at the mRNA (or cDNA) level, in transcriptomics, and at the protein level, in proteomics. In this short communication, arguments are given tor the development of proteomics as a necessary complement to the other two, prevalent today, approaches. Examples are given that demonstrate the power of such analysis and few perspectives are drawn.