Table 1. Summary of steps for fixation, embedding, and staining

Step	Reagent	Time	Temp./location	Repetitions
Primary fixation	Fixation solution for zebrafish embryos	2 hours	RT	1
Wash	0.1 M PBS	10 minutes	RT (hood)	3
Post-fixation	Dalton’s osmium and potassium dichromate buffer	1-2 hours	RT (hood)	1
Wash	H₂O	10 minutes	RT (hood)	3
Dehydration	30% ethanol	10 minutes	RT (hood)	1
	50% ethanol	10 minutes	RT (hood)	1
	70% ethanol	10 minutes	RT (hood)	1
	90% ethanol	10 minutes	RT (hood)	1
	96% ethanol	10 minutes	RT (hood)	1
	100% ethanol	10 minutes	RT (hood)	3
Infiltration	100% propylene oxide	20 minutes	RT (hood)	2
	1:1 embedding resin:propylene oxide	1 hour	RT (hood)	1
	Embedding resin	12-18 hours	RT (hood)	1
Prefill embedding mold bottom	Embedding resin	12 hours	60ºC (oven)	1
Embedding of embryo	Embedding resin		RT (hood)	1
Polymerization		at least 24 hours	60ºC (oven)	1
Contrast staining	0.5% uranyl acetate	30 minutes	Ultrastainer	1
Contrast staining	3% lead citrate	2 minutes	Ultrastainer	1