This book provides a critical overview of the advances being made towards overcoming biological barriers through the contribution of nanosciences and nanotechnologies. Overcoming these barriers is of primary importance for solving the problems of many current drugs and vaccines and it is also especially relevant for the commercial exploitation of new therapeutic strategies i.e. gene and cellular therapies. Despite important information that has been covered in recently published books related to nanomedicine (mainly oriented to technologies and applications), there is still an important gap related to the relationship between the chemical properties of nanobiomaterials and their interaction with the biological environment. Thus, this comprehensive new book that is presented with a clear and organised structure dedicated to the different biological barriers relevant for drug delivery applications will focus on (i) mechanistic issues related to the interaction between drug delivery systems and biological barriers and (ii) the analysis of the critical factors determining the efficacy of nanobiomaterials for specific applications. Moreover, this field has become highly multidisciplinary over the last decade, leading to the development of new products, as well as to significant advances from the regulatory point of view. Moreover, this book will also provide an up-to-date view on the clinical relevance of nanomedicine and on its possible impact on global health.