Chirality is a fundamental property of molecules and materials leading to very interesting optical activity effects. Classical optical effectivity effects such as optical rotation and circular dichroism have been known for many years and are of crucial importance to investigate the structure of molecules and to elucidate the secondary structure of biomolecules. Other optical activity effects also exist, both in linear and nonlinear optics, and are becoming increasingly important. Furthermore, new chiral materials based on nanoscale building blocks show very peculiar and new optical effects that can have important applications. The 16 papers in this feature issue focus on several new aspects of the role of chirality in optical phenomena in a variety of materials.