Target accuracy. Concepti dissected a few hours after ultrasound-guided microinjections of a 13.8 nL volume containing 3 μm diameter fluorescent beads. In these examples, there were few (e.g. arrows in A&D) or no beads considered off-target (e.g. B&C). The ectoplacental cone region was targeted in (A) at E6.5 and (B) at E7.5. At E7.5, the exocoelomic cavity (C) and amniotic cavity (D) were also targeted. AC, amniotic cavity; EPC, ectoplacental cone region; Exo, exocoelomic cavity.