Staining of mouse embryo --- lacZ
1. Fix embryos in fixing solution (0.5% glutaraldehyde, 1.25 mM EGTA, 2 mM MgCl2, in PBS). For large embryo, include 2-4% paraformaldehyde.

2. Fix for 15-30 minutes on ice for small embryos, 30 mintes to several hours for large embryos.

3. Rinse with PBS for 15-30 minutes with several changes of PBS.

4. Stain with PBS containing 1 mM MgCl2, 5 mM K4[FeII(CN)6], 5 mM K3[FeIII(CN)6], 0.02% NP-40, 0.01% Na deoxycholate, plus 1 mg/ml X-gal. X-gal staining solution should be warmed to 37 C for 5-10 minutes before use.

6. Incubate at room temperature or 37 C in dark until desired level of staining is observed (several hours to overnight). Stop staining by washing several times with PBS.

7. Store in PBS at 4 C.