Book excerpt: European banking supervision, also known as the Single Supervisory Mechanism, is the first and arguably the main component of European banking union. In late 2014, the European Central Bank became the supervisor for the region's largest banking groups; the ECB also oversees the supervision by national authorities of smaller banks. This Blueprint is the first in-depth study of how this ground-breaking reform is working in practice. Despite teething troubles and occasional misjudgements, this assessment finds that overall European banking supervision has been effective, demanding and broadly fair, at least for the banks under the ECB's direct watch. Even so, achieving a truly single market in banking services will require more time, further supervisory initiatives and new Europe-wide regulatory and legislative steps.