  This paper summarises the potential of the LISA mission to constrain the
expansion history of the universe using massive black hole binary mergers as
gravitational wave standard sirens. After briefly reviewing the concept of
standard siren, the analysis and methodologies of Ref. [1] are briefly outlined
to show how LISA can be used as a cosmological probe, while a selection of
results taken from Refs. [1,2] is presented in order to estimate the power of
LISA in constraining cosmological parameters.
