In order to meet these challenges innovative thinking is required. Over the past several years, the metrology community has been embracing the concept that if a given measurement technology cannot meet all of the given requirements, then maybe using data from multiple metrology technologies and combining it in a clever way can provide a better end result. This is referred to as hybrid metrology. Additionally, since there are so many different metrology technologies existing today (likely many more choices than in any other sector, such as etch or lithography), how does one best leverage obtaining the best results given so many choices? Consideration of all possibilities, determining what technology to use when and whether it can be used alone or in tandem with other technologies, is called holistic metrology. Both of these concepts were combined to describe this special section. This is an ever-growing area of exploration in metrology and has many more facets than a single special issue can cover. All fourteen papers are related in some way to holistic/hybrid metrology with a particular focus on the use of unconventional approaches.