In mathematics, the moduli stack of elliptic curves, denoted as M 1 , 1 {\displaystyle {\mathcal {M}}_{1,1}} or M e l l {\displaystyle {\mathcal {M}}_{\mathrm {ell} }} , is an algebraic stack over Spec ( Z ) {\displaystyle {\text{Spec}}(\mathbb {Z} )} classifying elliptic curves. Note that it is a special case of the moduli stack of algebraic curves M g , n {\displaystyle {\mathcal {M}}_{g,n}} . In particular its points with values in some field correspond to elliptic curves over the field, and more generally morphisms from a scheme S {\displaystyle S} to it correspond to elliptic curves over S {\displaystyle S} . The construction of this space spans over a century because of the various generalizations of elliptic curves as the field has developed. All of these generalizations are contained in M 1 , 1 {\displaystyle {\mathcal {M}}_{1,1}} .