Ras proteins are proto-oncogenes that are frequently mutated in human cancers. 
Three closely related isoforms, HRAS, KRAS and NRAS, are expressed in all cells 
and have overlapping but distinctive functions. Recent work has revealed how 
differences between the Ras isoforms in their trafficking, localization and 
protein-membrane orientation enable signalling specificity to be determined. We 
review the various strategies used to characterize compartmentalized Ras 
localization and signalling. Localization is an important contextual modifier of 
signalling networks and insights from the Ras system are of widespread relevance 
for researchers interested in signalling initiated from membranes.