Biologics, which target cytokines, have become increasingly popular for the treatment of refractory skin diseases, e.g., psoriasis and atopic dermatitis. The clinical response rates have been considerably improved by biologics compared with conventional topical and oral treatments. The results of clinical trials and experiences in daily practice with these drugs have provided valuable information pointing to other potential avenues of approach, illustrating the “bedside to bench” concept. Specific cytokine-targeted therapies have informed our understanding of the immunopathogenesis of skin diseases. This deeper understanding has stimulated drug development for refractory skin diseases. Biologics, however, are very expensive and must be carefully prescribed under the appropriate conditions. Chapter 1 Jaks And Stats Chapter 2 Jak Inhibitors Chapter 3 Jak Inhibitors and Hair Growth Chapter 4 Jak Inhibitors and Psoriasis Chapter 5 Jak Inhibitors and Atopic Dermatitis Chapter 6 Jak Inhibitors in Vitiligo and other Inflammatory Skin Diseases End.