For years, the suspicion has been around that pfaffian functions, as defined by Khovanskii in his work on fewnomials, are more general than the notion of pfaffian chains commonly used today. Recent work by Scanlon and Freitag in differential algebra has confirmed this suspicion. This leads to a more general notion of pfaffian chain, called nested pfaffian chain. (Ongoing work with Siegfried van Hille and Gareth O. Jones)