Climate Bonds Initiative (CBI), the first organisation worldwide to create a Green Taxonomy, has structured a comprehensive course to overview existing classification systems. This Deep-Dive presents the various approaches that have been developed as of now and the different objectives that are being sought through these instruments. It also provides an international overview and comparison by presenting global taxonomy developments based on the CBI’s experience developing its taxonomy and supporting other significant taxonomies worldwide. Additionally, it aims at helping market participants and other stakeholders better understand these tools, their usage, structure, etc., and help policymakers and the regulatory community in their reflections on the pertinence of classification systems. This training does not intend to prepare the audiences to develop their own taxonomies but to understand these instruments’ structure, objective, and use.