The dry dye Oil red O is used for the preparation of a staining solution that can be used for the detection of lipids in histological cryo sections.

Instructions:
a. Reagent preparation: Prepare Oil Red O stock solution, dissolve 0.5g Oil Red O in 100mL 98% isopropanol; for working solution, mix 24mL of stock solution with 16mL of distilled water, filter and use. Also prepare Mayer's hematoxylin stain and 1% lithium carbonate solution.
b. Operation steps:
1. Cut frozen tissue sections with a thickness of 10µm and dry them at room temperature for 10 minutes;
2. Use a liquid antifouling pen to draw along the area around each section;
3. Add 1mL of Oil Red O working solution, incubate at room temperature for 10 minutes (for heart and liver sections, incubation for 5 minutes is recommended; for muscle sections, incubation for 10 minutes), and wash with water;
4. Stain with Mayer's hematoxylin stain for 2 minutes and wash with water;
5. Blue in lithium carbonate solution for 30 seconds to 1 minute, wash with water, ((d) (e) optional, this step can show cell nuclei and tissue morphology, but will interfere with lipid quantification);
6. Seal with aqueous mounting medium;
7. Observe and photograph under an optical microscope. Stained sections should be photographed within 24 hours to avoid precipitation of Oil Red O dye.