Ah, one of my favourite questions. Most physicists prefer the answer 'primordial star', 'singularity' or as I used to call it, G.O.M.E (gravitationally [as in scalar] emitting massive entity).
There was supposedly a point of compact fractals or super-symmetric strings (vibrating nodes) that had not yet taken the form of space and time, nor the entity of manifolds…and therefore the universe as we know it was not established until quantum uncertainly perturbation occurred (otherwise known as spontaneous symmetry breaking).
You are well within your rights to inquire as to what came before, and many individuals become nervous when this question is posed, tending to dismiss it with answers such as ‘there was no before’ or ‘it is impossible to imagine a before’.
Physically this is true; but mathematically, it is not. Try to come up with some ideas yourself... What do YOU think existed ‘before’ the current universe had existed- what do you think the properties this meta-manifold or singularity would have been like?