Non-Hermitian systems bare some exceptional physics like the so-called exceptional points (EPs). We previously studied the merging of EPs in a parity-time symmetric system with zero-index materials (Read more). By establishing a non-Hermitian effective medium theory, we have well explained the emergence of EP rings from the perspective of effective media (Read more). We pointed out that traditional Maxwell-Garnett theory is not sufficient to describe a non-Hermitian composite and corrections must be made (Read more). We also proposed a theory to build pseudo-Hermitian systems with perfectly balanced loss and gain (Read more).