In the early nineties, at the initiative of Sinha and financial support of Shah and Liski (from their respective Research Project Funds), the authors - inspired by their similar research interests - started collaborative research at various institutions mostly in pairs and triplets. It took more time and efforts on the part of MandaI to visit the others at regular intervals and keep track of their common as well as diverse research areas and merge his own. From this collaborative work, the concept of this monograph took a preliminary shape only last year and serious efforts were started to combine diverse avenues into one. Admittedly, it took more time than expected to converge to a common platform regarding the contents and broad coverage of the topics to be included. We were mostly guided by our own common research interests spanning over the last ten years. That covered optimal designs in both discrete and continuous settings. Availability of huge published literature in various statistical journals on the broad theme of optimal designs has made our task quite interesting and stimulating. We hope our readers will be as excited and delighted to read the monograph as we have been in our efforts to write it.