Outperforming activity of Mn4Ca cluster, existing in biological photosynthetic organism have continued to inspire to develop the efficient Mn based water oxidation catalysts. Over the decades, understanding of the key catalytic mechanism and mimicry of the active site of the Mn4Ca cluster have been main research interests. This critical issue gives an overview the findings from recent studies on the water oxidizing mechanism and stepwise structural evolution of the Mn4Ca cluster during Kok cycle. In addition, recent advances in the development of Mn-based electrocatalysts, particularly those that have the capacity to function at neutral pH, are also presented. (C) 2016 Elsevier B.V. All rights reserved.