The versatile buck-boost (VBB) converter has been extensively studied because of its advantageous features such as step-up/step-down voltage conversion ratio, high efficiency, low-ripple continuous input-output currents easy to regulate, and the possibility of controlling any converter variable. These interesting features make it an excellent candidate to be a power electronics building block (PE-BB). This article summarizes the state-of-the-art PE-BBs and briefly describes the topological changes, control techniques implemented, and applications for which the VBB converter has been used so far. Finally, the experimental tests show that the proposed PE-BB can perform exceptionally well in dc-dc, ac-dc, dc-ac, and ac-ac applications.