X-gal staining solution for Drosophila eyes

Recipe

0.2 M Na₂HPO₄	1.8 mL
0.2 M NaH₂PO₄	0.7 mL
5 M NaCl	1.5 mL
1 M MgCl₂	50 μL
50 mM K₃Fe(CN)₆	3 mL
50 mM K₄Fe(CN)₆•3H₂O	3 mL
H₂O	40 mL

Prepare staining solution buffer with the ingredients above. This solution is stable for months when stored at room temperature in a foil-wrapped container.
Prepare X-gal stock solution of 8% X-gal in DMF (N,N-dimethylformamide). Store in 50-μL aliquots at −20ºC.
When fresh X-gal staining solution for Drosophila eyes is needed, prewarm the staining solution buffer at 37ºC for 5 min. Add 8 μL of 8% X-gal stock solution per 300 μL of staining solution buffer. Prewarming decreases precipitation of X-gal crystals.