Yet another path towards replacement - or even additional, completely novel - organs is examined at EurekAlert!: researchers "have assembled different types of genetically engineered cells into synthetic microtissues that can perform functions such as secreting and responding to hormones, promising more complex biological capabilities than a single cell alone could produce. ... This is like another level of hierarchical complexity for synthetic biology. People used to think of the cell as the fundamental unit. But the truth is that there are collections of cells that can do things that no individual cell could ever be programmed to do. We are trying to achieve the properties of organs now, though not yet organisms. ... While the synthetic tissues today comprise only a handful of cells, they could eventually be scaled up to make artificial organs that could help scientists understand the interactions among cells in the body and might some day substitute for human organs. ... In principal, we might be able to build a stem cell niche from scratch using our techniques, and then study those very well defined structures in controlled environments."