Trends in Nature’s July top ten PDF downloads: 5 stem cell papers!

Maxine Clarke over at Nature’s Nautilus blog published Nature’s July top ten PDF downloads.
July was a particularly strong month for Nature concerning pluripotency and embryonic stem cells as 5 out of the 10 top ten downloads, that is 50% of the most popular articles are tinkering with stem cell biology. The other trend: microRNAs, 2 papers. I wonder which could be the last research trend that reached that maturity and which will be the next.