This is a Romanesco broccoli, and I think it's one of the most fascinating vegetables there is. Its structure is amazingly fractal in nature, and its self-similarity at different scales goes many levels deep.
I've been wanting to photograph one for a while, but I had never seen one in a supermarket until today.
Here's a shot including my hand to give you a sense of scale...
...and here are a couple of close-ups so you can see the remarkable fractal patterns...
