Choose leaves with thick veins and thick mesophyll for standby. Put 200mL water in a beaker, put 5g sodium carbonate and 7g sodium hydroxide in the water, and heat it on the fire. After boiling, put the leaves in a cup and cook for about 10min. In this process, the blade should be gently swung with tweezers to make the blade corrode evenly. Cut off the leaves after cooking, put them in a glass jar filled with clear water, brush off the leaves except the veins with a soft-bristled toothbrush (preferably a hard-bristled toothbrush) to expose the veins, then float them in a bleaching powder solution (that is, dissolve 8g bleaching powder in 40mL water and 6g potassium carbonate in 30mL boiling water), then mix and shake the two solutions evenly, cool them, add 100mL water, and filter them. After bleaching, the vein samples can be dyed into various colors as needed.