Multiferroics have been used to address fundamental questions in cosmology and particle physics. In the first, the fact that an individual electron is an ideal multiferroic, with any electric dipole moment required by symmetry to adopt the same axis as its magnetic dipole moment, has been exploited to search for the electric dipole moment of the electron. Using the designed multiferroic material (Eu,Ba)TiO 3, the change in net magnetic moment on switching of the ferroelectric polarisation in an applied electric field was monitored, allowing an upper bound on the possible value of the electron electric dipole moment to be extracted. This quantity is important because it reflects the amount of time-reversal (and hence CP) symmetry breaking in the universe, which imposes severe constraints on theories of elementary particle physics. In a second example, the unusual improper geometric ferroelectric phase transition in the hexagonal manganites has been shown to have symmetry characteristics in common with proposed early universe phase transitions. As a result, the hexagonal manganites can be used to run experiments in the laboratory to test various aspects of early universe physics. In particular, a proposed mechanism for cosmic-string formation has been verified, and aspects of cosmic string evolution are being explored through observation of their multiferroic domain intersection analogues.