Transformation optics which relies on the formal invariance of Maxwell’s equations under a spatial coordinate transformation, plays important roles in various branches of modern optics and technical application by providing schemes to tailor electromagnetic fields into desired spatial patterns. The concept development of transformation optics was reviewed and a briefly introduction was provided for the physical principles of transformation optics. Typical applications were discussed including invisibility cloaking, illusion optics and waveguiding and extensions on the manipulation of sonic waves, heat flows and quantum waves. Potential future developments of the concepts and applications of transformation optics were also discussed.