Firewood with pine cone formed inside the tree

From the Mildly Interesting subreddit, where the process is explained.

As a side note it is correct to write the word as 'pinecone' and not as pine cone as most people do (we even had to force auto correct to ignore the separated spelling for this note). 

We should have remembered that fact from elementary grammar class, but it was lost in the unused memory section of the brain therefore the title of this post reflects that unused memory.