1. A method for tracking and tracing items comprising the steps of; generating a group of unique codes in a computer implemented track and trace system, where each of said unique codes comprises a unique reference encrypted with a unique key, transferring said group of unique codes to an item marking location, marking each of one or more of said items with at least one of said unique codes, transferring one or more of said unique codes back to said computer implemented track and trace system, decrypting one or more of said unique codes, in said computer implemented track and trace system, with said unique key to obtain said unique references, creating one or more tracking records for one or more of said items marked with said unique codes, and storing said tracking records in one or more unique storage locations in said computer implemented track and trace system, creating a relation node for each of one or more of said items wherein said relation nodes are arranged in a tree structure having a parent node and at least one child node, and relationships between said relation nodes represent packaging relationships between said items, wherein one or more of said relation nodes are arranged for referring to said unique storage locations for said item represented by said relation node, and said unique references are unique references to said relation nodes, wherein one or more of said unique references are references to one or more of said unique storage locations via said relation nodes, wherein each of said unique references comprises a first level reference and a second level reference wherein said second level reference is unique within said first level reference, and wherein said first level reference corresponds to said group and said second level reference corresponds to a sequence number within said group.