Voom function from limma package and Normalization on counts data I know that Voom function from limma package from Bioconductor converts raw counts into log-CPM values and then Normalization is applied on that, with normalize.method argument.
I would like to know clearly

how this normalization is done (statistically) ?

normalization across samples and normalization across genes. But don't the know how it is done statistically.
I'd like to know answer for this myself. It seems the normalize.method argument is set to none by default. You can edit by looking at the methods in normalizeBetweenArrays. 
But how do I know if and when I have to use normalize.method in my analysis?
The output from voom is log2CPM of count values (adding 0.5 to them).