I have four replicates for early and late lactation stages each. I did rlog transformation of the htseq counts and did PCA as a QC step to know whether the biological conditions cluster together. I obtained the attached PCA plot. Now I have a confusion on the axis I have to look for. As in the image, on PC2 axis the early and late stages cluster among themselves, but on PC1 they don't not. Can anyone please advise me the axis I should consider first?. Thank you!