In this talk I introduce GW event GW190521 and describe its properties.
Then I will assume its association with the optical flare observed by the Zwicky Transient
Facility in an Active Galactic Nucleus (AGN). After giving some plausible explanation of this association,
I will move to possibility observing GW190521-like event(s) with LISA. LISA should detect few tens
of stellar-mass black hole binaries few years before the 3rd generation of ground-based GW