What people refer to as a challenge

That doesn't deter IBM, though. Apparently, its long-term goal is to essentially build an actual silicon version of the brain. As they put it, that means they need a chip system with ten billion neurons and hundred trillion synapses, which consumes one kilowatt of power and occupies less than two liters of volume. That's what people refer to as a challenge.

Here's the Gizmodo article: http://gizmodo.com/ibm-is-creating-an-entire-computing-architecture-based-1063836530