This is the introductory chapter of the book, which presents a snapshot of the current state of the art, critically reviewed, as it relates to the materials challenges facing low-temperature fuel cells. The book focuses on the emerging areas of interest, with a particular focus on alkaline exchange (or hydroxide exchange) membrane fuel cells. Two other specific areas must be mentioned in the chapter: the emerging fields of microbial fuel cells and microfluidic fuel cells. In some ways these two new fields can be considered embodiments of low-temperature fuel cells operating at the extreme size scales - microbial fuel cells have their genesis in the exploration of wastewater treatment in electrochemical and bioelectrochemical systems. These proposed applications are by their nature enormous in size, with reactor volumes measured in the tens of cubic meters (many orders of magnitude larger than the conventional low-temperature fuel cells).