Majority of the sRNA population in the cell are represented by only one copy. The y-axis represents the number of unique reads and the x-axis shows the number occurrences in each library. The reads occurring more than 10 times are not shown in the figure as they follow the same trend after 10.
Aryal et al. BMC Genomics 2012 13:682 doi:10.1186/1471-2164-13-682