An interesting open access review paper - the full thing is in PDF format only: "The development of materials and technologies for the assembly of cells and/or vesicles is a key for the next generation of tissue engineering. Since the introduction of the tissue engineering concept in 1993, various types of scaffolds have been developed for the regeneration of connective tissues in vitro and in vivo. Cartilage, bone and skin have been successfully regenerated in vitro, and these regenerated tissues have been applied clinically. However, organs such as the liver and pancreas constitute numerous cell types, contain small amounts of extracellular matrix, and are highly vascularized. Therefore, organ engineering will require the assembly of cells and/or vesicles. In particular, adhesion between cells/vesicles will be required for regeneration of organs in vitro. ... adhesive materials and technologies will work as 'glues' for assembling various kinds of cells. The adhesive materials should be degraded when cells themselves biosynthesize cell adhesion molecules ... Although integration of newly developed materials and technologies will be required for the regeneration of organs in vitro, this will ultimately lead to the creation of three-dimensionally engineered organs with functions similar to those of natural organs."