Abstract
In this introductory lecture I will highlight the role of correlations, fluctuations and clustering in nuclear systems under two conditions: in static nuclear matter and in the dynamic situation of heavy ion collisions. Both aspects will be discussed particularly with respect to the investigation of the nuclear symmetry energy.

In static systems it touches the question of the composition of nuclear matter as a function of density and temperature, which is important also in the astrophysical context of supernovae and in the neutron star crust. It can also influence nuclear structure observables, such as the nuclear mass radius.

Clustering is of large importance in the dynamical situation of heavy ion collisions. It is a ubiquitous feature of the experimental data and influences the interpretation of the data by transport theories. The treatment of clustering in transport theories is, however, one of the least well understood aspects. The formation of larger clusters (IMF) is largely triggered by fluctuations. The formation of these clusters depends on a realistic descriptions of fluctuations which goes beyond mean field theory, and may be different in different transport approaches. The formation of light clusters - up to the alpha particle - is not well described in this way, but depends strongly on correlations. These are perhaps best treated explicitly as distinct degrees of freedom. In the talk I will try introduce these questions which will undoubtedly be discussed in more detail in the talks of the meeting.