This issue of the Journal is mainly devoted to a specific, crucial topic in the field of histochemical research: how in situ technologies can be exploited to study tissue samples from patients with specific diseases. The final goal is on one hand a more accurate diagnosis; on the other, the identification of specific features that can: i) be followed and compared at different time points ii) provide hints on the natural history of the disease and iii) represent surrogate end-points for targeted molecular treatments. The European Journal of Histochemistry has always been particularly concerned with the molecular study of diseases in different tissues, and we had the privilege to publish recently several cuttingedge reports dealing with such a subject (Boniotto et al., 2003; Lanni et al., 2003; Maraldi et al., 2003; Munoz et al., 2003; Benkoel et al., 2004; Cremer et al., 2004; Rambotti et al., 2004;Trovato et al., 2004;Waltregny et al., 2004;Woodall and Graham, 2004)