Cut to the bone

This is a very, very thin slice of bone, stained with silver salts,  as seen down the microscope. Bone consists of multiple microscopic columns called osteons. Each column consists multiple concentric layers of bone cells, known as osteoblasts and osteocytes, organised around around a central tube called an Haversian canal through which run blood vessels. The canals are named after the 17th Century physician Clopton Havers, who first described them.

Just in case you think that I spend all of my time peering into the micro world, the "extra" shows a skein of wild geese flying over the house this afternoon.