1. Classification by Bottle Material: Glass, Plastic, Metal Glass dropper bottles: Their primary advantage is their chemical inertness, meaning they won't react with the contents. They're ideal for storing active ingredients (such as vitamin C serums and retinol serums) or corrosive liquids (essential oils and pharmaceutical solvents). Clear glass dropper bottles: Suitable for products that don't require light protection (such as regular toners and serums), making it easier to see how much is left. Dark glass dropper bottles (amber, cobalt blue): With built-in UV protection, they effectively block UV rays, preventing oxidation and deterioration of ingredients, making them the best choice for light-sensitive products. Plastic dropper bottles: Their primary advantages are lightness, drop resistance, and low cost, making them suitable for daily use and various office settings. However, care should be taken with the material to avoid chemical intrusion. PP dropper bottles: They offer excel...