Advances in cell spheroid technology towards complex tissue formation guided by microfabrication and biomaterial innovations.

Spheroids have become a de facto model three-dimensional tissue for studying various biological phenomena. While the technology to produce spheroids has become highly accessible and is routinely used by researchers, it has quite a long history, going through successive advances incorporating various scientific and engineering principles to acquire efficiency, accuracy, and high-throughput capability. More recently, the spheroid technology is advancing towards recapitulating complex physiological features, especially introducing extracellular components via biomaterials to more accurately portray tissue microenvironment. This review introduces and chronicles the advancement in spheroid technology in historical perspective, highlighting the key attributes of various techniques with notable examples. The spheroid technology is for convenience divided into three different generations, based on the era and the level of technological sophistication.