Mouse Embryos (IMAGE) RIKEN Caption Mouse embryos. Left: embryo placed in phosphate buffered saline (PBS) after fixation with 4 percent paraformaldehyde (PFA). Right: embryo incubated in ScaleA2 solution for 2 weeks after fixation with 4 percent PFA. Credit RIKEN Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.