It is really remarkable that only one century ago, two out of 10 people in the world were living in urban areas. In the least developed countries, this proportion was as low as five per cent, as the overwhelming majority was living in rural areas. The world has been rapidly urbanizing since then and, in some countries and regions, at an unprecedented pace. It was only two years ago that humankind took a landmark step when, for the first time in history, urban outnumbered rural populations. This milestone marked the advent of a new ‘urban millennium’ and, by the middle of this century, it is expected that out of every 10 people on the planet, seven will be living in urban areas.