Artificial intelligence is growing up fast, as are robots whose facial expressions can elicit empathy and make your mirror neurons quiver.
Octopuses have hundreds of suckers, each one equipped with its own ganglion with thousands of neurons. These 'mini-brains' are interconnected, making for a widely distributed nervous system. That is why a severed octopus arm may crawl on its own and even pick up food.
In the human mind, the number of possible connections that can be made between neurons greatly exceeds the number of atoms in the universe.
A typical neuron makes about ten thousand connections to neighboring neurons. Given the billions of neurons, this means there are as many connections in a single cubic centimeter of brain tissue as there are stars in the Milky Way galaxy.
The human brain has 100 billion neurons, each neuron connected to 10 thousand other neurons. Sitting on your shoulders is the most complicated object in the known universe.
We are all now connected by the Internet, like neurons in a giant brain.
Essentially, all expressions of human nature ever produced, from a caveman's paintings to Mozart's symphonies and Einstein's view of the universe, emerge from the same source: the relentless dynamic toil of large populations of interconnected neurons.
The brain is the most complicated organ in the universe. We have learned a lot about other human organs. We know how the heart pumps and how the kidney does what it does. To a certain degree, we have read the letters of the human genome. But the brain has 100 billion neurons. Each one of those has about 10,000 connections.
Your brain is built of cells called neurons and glia - hundreds of billions of them. Each one of these cells is as complicated as a city.
For me, consciousness is the most interesting unsolved problem of science, and, in fact, we may never know what it is about a particular arrangement of neurons that gives rise to consciousness. Our consciousness, like the air we breathe or like the passage of time, is central to our existence as intelligent beings.