Molecular computing is a rapidly growing subarea of natural computing. On the one hand, molecular computing is concerned with the use of bio-molecules for the purpose of actual computations while, on the other hand, it attempts to understand the computational nature of molecular processes going on in living cells. The book presents a unique and authorative state-of-the-art survey on current research in molecular computing: 30 papers by leading researchers in the area are drawn together on the occasion of the 70th birthday of Tom Head, a pioneer in molecular computing. Among the topics addressed are molecular tiling, DNA self-assembly, splicing systems, DNA-based cryptography, DNA word design, gene assembly, and membrane computing.