Queer theory is a field of Gender Studies that emerged in the early 1990s out of the fields of gay and lesbian studies and feminist studies. Heavily influenced by the work of Michel Foucault, as well as by Jacques Derrida and other deconstructionists, queer theory builds both upon feminist challenges to the idea that gender is part of the essential self and upon gay/lesbian studies' close examination of the socially constructed nature of sexual acts and identities. Whereas gay/lesbian studies focused its inquiries into "natural" and "unnatural" behavior with respect to homosexual behavior, queer theory expands its focus to encompass any kind of sexual activity or identity that falls into normative and deviant categories.