B Cell Development and Its Deregulation to Transformed States at the Pre-B Cell Receptor-Expressing Pre-BII Cell Stage -- Gene Expression Patterns in Human and Mouse B Cell Development -- New Insights into the Phenotype and Cell Derivation of B Cell Chronic Lymphocytic Leukemia -- Chronic Lymphocytic Leukemia: Molecular Genetics and Animal Models -- What Do Somatic Hypermutation and Class Switch Recombination Teach Us About Chronic Lymphocytic Leukaemia Pathogenesis? -- Chronic Lymphocytic Leukaemia: A Review of the Immuno-architecture -- Clinical and Laboratory Parameters That Define Clinically Relevant B-CLL Subgroups -- Differential Effects on CLL Cell Survival Exerted by Different Microenvironmental Elements -- Genotypic Prognostic Markers -- Chronic Lymphocytic Leukaemia: Clinical Translations of Biological Features. Chronic lymphocytic leukaemia (CLL) is the most common leukaemia in the Western world. It is also the prototype of B-cell chronic lymphoid malignancies and of their ramifications within the fields of hematology, immunology and oncology. For a long time the Cinderella of lymphoid malignancies CLL has now become the focus of major interest and an increasing number of investigators from different areas, including genetics, molecular biology, basic and applied immunology are becoming actively engaged in the investigation of CLL. Clinicians are considering CLL as a very interesting target of many projects which aim at translating the new and exciting developments of basic science into effective new approaches to the patient.