I will give an introduction to the Ax-Schanuel property for
differential equations and explain why it is relevant to model theory of
differential fields. I will start with the classical Ax-Schanuel inequality for
the exponential differential equation and generalise it to linear differential
equations of any order with constant coefficients. Then I will give a complete
axiomatisation of the first order theories of those equations and show that the
generalised Ax-Schanuel inequalities are adequate for them.