Scientists from across the globe met in Switzerland last month for the launch of the Human Brain Project. However, building a computer to simulate the human brain is no easy task: in each cubic millimeter of brain tissue there are around 100,000 neurons, and each one makes contact with around 10,000 other neurons. Markus Diesmann, from Germany’s Jülich Research Centre, provides insight into the complexities surrounding this epic undertaking. He speaks about his work on simulating a circuit of the whole-brain network and discusses how specialized software can help represent the neurons and synapses of the full circuit.