After reviewing the formalism in quantum field theory, I will discuss the real-part interferences in Higgs and top physics. And I will explain more recent developments on the striking phenomena induced from the imaginary-part interference; New resonance shapes -- pure dips, nothingness and enhanced pure peaks -- are produced and collider searches of heavy Higgs bosons are crucially impacted. The pure resonance dip is a particularly interesting signal as they can shed light on complex resonance searches based on the current searches and the modified narrow width approximation.