The importance of invasion in the complex process of metastasis, although now well established, has been studied with increasing molecular detail due to the development of robust in vitro experimental assays. In this issue of Cancer Research, we highlight a paper published by George Poste and colleagues that compared and contrasted several different invasion assays. The authors concluded that various barriers impose different selective pressures and that simply enriching for invasive ability did not necessarily translate into greater metastasis efficiency. Although perhaps obvious now, these findings were surprising when they were published. Certainly, the data highlight the importance of tumor cell-microenvironment interactions and the necessity to interpret experiments taking the context into consideration.