Synthetic Biology is the engineering of biology: the deliberate (re)design and construction of novel biological and biologically based systems to perform new functions for useful purposes, that draws on principles elucidated from biology and engineering (source: ERASynBio). Synthetic Biology is an emerging and promising research area with the potential to have a strong impact on future innovation and technological progress that is beneficial for the economy and for society as a whole. Synthetic Biology is at the intersection of engineering, bioscience, chemistry, and information technology. It provides concepts and toolboxes that open the way to a wide range of biotechnological applications in health, environment, bioenergy and fine chemical synthesis. It also allows to ask some fundamental questions in a new and sometimes more efficient way. This lecture will provide a multifocal definition of Synthetic Biology and of its scientific contents. It will discuss of the epistemological conditions of its recent emergence. It will finally cover a wide ground of applications of Synthetic Biology through specific examples.