Since the discovery of non-coding, small, highly structured, satellite RNAs 
(satRNAs) and viroids as subviral pathogens of plants , have been of great 
interest to molecular biologists as possible living fossils of pre-cellular 
evolution in an RNA world. Despite extensive studies performed in the last four 
decades, there is still mystery surrounding the origin and evolutionary 
relationship between these subviral pathogens. Recent technical advances 
revealed some commonly shared replication features between these two subviral 
pathogens. In this review, we discuss our current perception of replication and 
evolutionary origin of these petite RNA pathogens.