The 9th International Conference on Lymphatic Tissues and Germinal Centres in Immune Reactions was held in Oslo, 9-14 August, 1987. These conferen­ ces, by the regular devotees just referred to as the germinal centre con­ ferences or GCC, have been held regularly at roughly three-year intervals since 1966. The credo of these conferences is "in vivo veritas", signifying that investigating components, like molecules and cells, only gives partial truth. The components must ultimately be explored in their natural con­ text, to see how they interact with other parts and are integrated to a whole. To the biologist it is obvious that the world must be investigated at many different levels of organization. At each level the patterns observed represent just some of many possible ways of putting together the elements of the lower levels. These patterns are not predetermined, but the results of evolution, i.e. of a history in which stochastic processes play a major role. The organic world can therefore not be torn apart and then reconstructed from basic principles alone. This realization is often expressed as the whole being more than the sum of its parts.