Usually after a routine PCR attempt, researchers would find that their PCR has failed to amplify the intended target into the correct product. The reasons for this failure can be a few, top on the list, is the complexity of PCR target. Specifically, when the target sequence, or the primer sequence, contains high GC content >60%, or if the target sequence contains a secondary structure, the targets are difficult to denature, leading to failed PCR. The solution to this problem is to use the PCR for Difficult Targets. This type of PCR is featured by using polymerases that are better able to handle the high complexity targets, or additives such as the PCR Enhancing Reagent.