The naïve hTSC-derived 3D STB-like cells exhibited a cyst-like morphology typical for 3D STBs (Okae et al., 2018; Figure 3H), and expressed the STB markers hCG and SDC1 based on immunofluorescence and qRT-PCR analysis (Jokimaa et al., 1998; Strumpf et al., 2005; Figure 3I–K). Here, SDC1 is linked to cyst.