At leading twist, parton distributions (i.e. PDFs, FFs, GPDs and TMDs) 
can be interpreted as giving the probability of finding a quark or a gluon with given polarization, 
momentum and/or position inside a nucleon. From a global perspective, they can be seen as different 
projections of a single more general object: the quark and gluon phase-space density. We present selected 
results covering various aspects of the nucleon internal structure and discuss the connection with parton 
orbital angular momentum, a key quantity to understand the origin of the proton spin.