Block within another block In drupal 7, I want to render block into another block, for example block-1 into block-2. 
I guess I should put some PHP code into block-2, but I don't know what the code could be?
Based on Ashlars's comment.

A minipanel, provided by Panels, is for anyone not used to Panels, essentially a block, that supports internal layouts. You can use a mini-panel to wrap several different blocks (and many other things, views, nodes, etc) into a single "block".

Unfortunately, I must admit that documentation is scarce on this topic. I will refer you to this other question: looking for a good mini panels tutorial.