Danish-born physicist Per Bak, a professor at Imperial College in London, opened ICTP's workshop on Self-Organized Criticality and Phase Transitions in Driven Systems with a lecture outlining his views on homogeneity and non-homogeneity in the universe. Bak, a frequent visitor to the Centre, is one of the founding fathers of the science of self-organised critical systems, which emphasises the deeply disruptive, yet self-correcting, forces-such as earthquakes and volcanic eruptions-that seem to drive the Earth's "metabolism." Although Bak's theory remains a controversial tool for understanding the behaviour of natural systems, it has gained a great deal of notice in the field of economics, especially for deciphering the sometimes volatile behaviour of the stock market. Bak's work has attracted the attention of several public officials, including U.S. vice-president Al Gore.