When we first wrote about Quantum Paper (the internal name for the material in Material Design), we noted that Google was anticipating a series of updates to its own apps between the introduction and completion of the new design direction - updates which would bring the apps a bit closer to the new design style in a progressive fashion, so that the apps wouldn't undergo fundamental transformations overnight.
Looking back, it is now obvious that Google+ was our first taste of material design, followed by Google's editing apps like docs and sheets.
Exclusive: Google Prepping Play Store Update That's One Step Closer To Material With Beautiful New Listing UI was written by the awesome team at Android Police.