Abstract: A combined scalable in vitro differentiation and assay system based on human blastocyst-derived stem (hBS) cells or cells derived from hBS cells is provided. This system makes it possible to merge both the differentiation and the assay parts of the system into one. The advantage of the combined assay system is that the hBS cells or the cells derived from hBS cells in the differentiation system are directly applicable for assays, in a large variety of assay units, such as different multiwell plates. The system offers a major improvement compared to the prior art, since the cells are differentiated in the same format as when further being subject to analysis. The starting cell material can be homogenously distributed across a variety of different plates, for use and can be cultured when attached, when semi-attached or when in suspension.