Image Thumbnail in Google Mobile Search results

[RetailClicks]

HI all,

We can see that Google is now showing thumbnails of products in the search results on mobile.
Very nice, but...

What are specs of our snippets to show? Cause i see it at other search results of websites, but not ours?
Please help us out.

Thanks!
Jeroen

http://searchengineland.com/google-mobile-search-results-now-showing-images-snippets-258919

[KevinBudzynski]

I know that there is a thumbnail meta tag:  --but I doubt this populates it. My gut tells me that Google will do this automatically.

On seorountable, they speculate it may come from product schema/market and the rich snippets Google shows for them.