The characterisation of (nano) porous materials has engaged the attention of a large community of physical scientists over several decades. For example a series of tri-annual meetings* has been devoted solely to this

topic since the early 70’s, and characterisation generally forms an important section in many other meeting series centred around problems related to adsorption and adsorbents amongst which may be mentioned the Fundamentals of Adsorption series* started in 1983, a series of meetings on the theme of heterogeneity in adsorption,** held in Poland since 1992, and a more recent series on porous materials held in Princeton*** and in the Pacific Basin countries.****

It is reasonable to ask — why is this not a solved problem? Part of the answer lies in the wide and ever increasing variety of porous materials, part in the randomness of many materials and part in the subtlety and complexity of matter at the nanoscale. Moreover, porous materials find many applications in industry, as well as being ubiquitous in the natural world, so there is a strong motivation behind the sustained interest they evoke.