This book investigates recent progress in synthesis of soft, hard and hybrid Janus structures and looks at processing strategy, such as emulsion polymerization, microfluidics, co-jetting and seeded growth. Also reviewed are both the experimental and theoretical studies on the unique self-assembly behaviour of Janus particles.Janus particles are special types of nanoparticles whose surfaces have two or more distinct physical properties. These two hemistructures are of different composition and functionality, offering promising potential for application through the multiple combinations possible -- areas in which Janus structures can be applied include drug delivery, magnetic biomarkers, bactericides, tailored plasmon resonance, photocatalysis and nanoengines. Encapsulating a wealth of research on Janus structures, this review of the literature is specifically designed to benefit graduate students and researchers in the fields of chemistry, materials science, engineering, biotechnology and applied physics, as well as practitioners in these industries.