Natural Computing is a field of research in Computer Science aimed at reinterpreting biological phenomena as computing mechanisms. This allows unconventional computing architectures to be proposed in which computations are performed by atoms, DNA strands, cells, insects or other biological elements. Membrane Computing is a branch of Natural Computing in which biological phenomena of interest are related with interactions between molecules inside cells. The research in Membrane Computing has lead to very important theoretical results that show how, in principle, cells (...) could be used to solve any (computable) computational problem with performances that cannot be obtained by conventional computers. However, the implementation of a cell-based computational architecture seems not easily achievable. On the other hand, models of Membrane Computing have found an alternative application to the description of biological systems, with the aim of developing simulators and other analysis tools for the study of biological problems. (shrink)