Double Field Theory (DFT) and Exceptional Field Theory (EFT), collectively called ExFTs, have proven to be a remarkably powerful new framework for string and M-theory. Exceptional field theories were constructed on a case by case basis as often each EFT has its own idiosyncrasies. Intuitively though, an E n−1(n−1) EFT must be contained in an E n(n) ExFT but how this works has been unclear since different EFTs are not related by reductions but by rearranging degrees of freedom. In this paper we propose a generalised Kaluza-Klein ansatz to relate different ExFTs. We then discuss in more detail the different aspects of the relationship between various ExFTs including the coordinates, section condition and (pseudo)-Lagrangian densities. For the E 8(8) EFT we describe a generalisation of the Mukhi -Papageorgakis mechanism to relate the d = 3 topological term in the E 8(8) EFT to a Yang-Mills action in the E 7(7) EFT. i d.s.berman@qmul.ac.uk ii r.otsuki@qmul.ac.uk 1 We have been explicit in specifying the continuous groups as they are not quite the discrete T-and U-duality groups. We shall henceforth drop the R and leave it implicit (see [1] for a discussion of how these dualities appear in ExFTs).2 See also [12,13] for progress on the n = 9 case (the first instance where the extended spacetime is infinite-dimensional). 3 See also [22] which studied the relation between the M-theory and Type IIB solutions of the same EFT.