Nowadays there are special plastic bags made specifically for storing breast milk in the freezer. However, these storage bags are not ideal for storing milk at work because they might leak, tear or get contaminated as you transport the milk back home. If you must use these bags, place them in tightly sealed plastic food containers to avoid tearing and contamination. Another option is to store the milk directly in hard plastic containers that have a tight lid. Avoid glass storage containers because they can break. Remember to always indicate the date and time the milk was expressed on the storage container. This will help you make sure that your baby feeds on the oldest milk first.