Kang Xu , and Guosheng Shao*

In this issue,we are pleased to carry on the theme of Frontier Outlook(https://doi.org/10.1002/eem2.12313) to publish the invited contribution “The Transference Number” from Prof. Balsara and colleagues.As one of the“triad properties”required to fully describe an electrolyte(i.e., conductivity, diffusivity, and transference number), the last proved to be the most challenging quantity that can be accurately and reliably determined,as evidenced by the widely scattered data from different techniques, as well as the associated debates in recent literature.Applying Newman’s concentrated electrolytes, Balsara et al. showed us the importance of reference frame for transference number measurement, and elaborated how to differentiate the transference numbers approximately or rigorously determined.