for example alternative splicing - more variability for making more proteins from 1 gene. for example, you have gene with introns 1,2,3. 1st time you splice I1, I2 and I3 stays in the gene (becoming exon now). 2nd time splice I1, I3 and leave I2 in the gene -> different protein. there are lot of combinations and this is actually principle of making a lot out of almost nothing.