Here we review recent developments and trends in sample preparation, pre-fractionation, chromatography and mass spectrometry contributing towards the ultra-sensitive global analysis of proteins. Highly sensitive MS-based proteomics is not only beneficiary for the proteome analysis of single cells, an aim which is getting into reach, but also clearly relevant for the analysis of (a) subcellular organelles, (b) specific low-abundant cell-types such as adult stem cells, and (c) smaller but more homogeneous cell populations sorted or dissected from (diseased) tissue.