Chromatin is a highly structured nucleoprotein complex made of histone proteins 
and DNA that controls nearly all DNA-dependent processes. Chromatin plasticity 
is regulated by different associated proteins, post-translational modifications 
on histones (hPTMs) and DNA methylation, which act in a concerted manner to 
enforce a specific "chromatin landscape", with a regulatory effect on gene 
expression. Mass Spectrometry (MS) has emerged as a powerful analytical strategy 
to detect histone PTMs, revealing interplays between neighbouring PTMs and 
enabling screens for their readers in a comprehensive and quantitative fashion. 
Here we provide an overview of the recent achievements of state-of-the-art mass 
spectrometry-based proteomics for the detailed qualitative and quantitative 
characterization of histone post-translational modifications, histone variants, 
and global interactomes at specific chromatin regions. This synopsis emphasizes 
how the advances in high resolution MS, from "Bottom Up" to "Top Down" analysis, 
together with the uptake of quantitative proteomics methods by chromatin 
biologists, have made MS a well-established method in the epigenetics field, 
enabling the acquisition of original information, highly complementary to that 
offered by more conventional, antibody-based, assays.