Manganese is an essential metal that participates as a co-factor in a number of critical biological functions such as electron transport, detoxification of free radicals, and synthesis of neurotransmitters. Like other heavy metals, high concentrations of manganese are toxic. For example, chronic overexposure to manganese leads to movement disorders. In order to maintain this balance between being an essential participant in enzyme function and being a toxic heavy metal, a rich biology has evolved to transport and store manganese. Paramagnetic forms of manganese ions are potent MRI relaxation agents. Indeed, Mn2+ was the first contrast agent proposed for use in MRI. Recently, there is renewed interest in combining the strong MRI relaxation effects of Mn2+ with its unique biology in order to expand the range of information that can be measured by MRI. Manganese Enhanced MRI is being developed to give unique tissue contrast, assess tissue viability, act as a surrogate marker of calcium influx into cells and trace neuronal connections. In this article we review recent work and point out prospects for the future uses of manganese enhanced MRI.