A grid format is best accomplished with responsive CSS. The browser will reflow the number of columns based on available width. Position relative and float left or right will accomplish most of it. It’s essential that each featured image be the exact same size. As output if not as uploaded.

The enlarged image view would be accomplished with jQuery and AJAX. You could try looking at gallery plugins, either WP or jQuery. In particular ones that work with arbitrary HTML instead of just images so you can utilize output for posts.

Today I was still trying to solve this and I found this own post of mine :-/

So, i think i understand it, but… it is also necessary to link each new post to the archives grid, right?

How is this done?

And about the plugins, any WP or jQuery plugins would do it?

Thank you for your reply!