Monoclonal antibodies and therapeutic proteins exhibit high molecular complexity and are sensitive to changes: temperature, agitation, buffer conditions, concentration, and other stresses, which might affect their safety, efficacy, stability, and clinical performance. Therefore, proper Critical Quality Attributes characterization and selection allows to understand structure and function relationships in order to assess possible risks. ICH Q6B recommends diligent critical quality attributes characterization, related to physicochemical characterization, binding and biological activity, quantity, and purity. Using high-resolution methods, orthogonal methods, and new technologies is advised whenever possible. In general, ICH Q6B recommends: