It is an important problem to understand whether the matrix model of M-theory contains the splitting(-joining) interactions of membranes. In the talk, I will discuss the splitting processes in the pp-wave matrix model, which are certain tunnelling processes. After a brief discussion of the relation to the ABJM theory via the AdS/CFT correspondence, I will show that the BPS instanton equations governing such processes are equivalent to the three-dimensional Laplace equation, under an approximation which is valid when the matrix size is large. I will further show that the solution which corresponds to a splitting process is not defined on R^3, but rather on a space which is constructed by stitching two R^3's, in a manner analogues to the construction of Riemann surfaces. I will also show plots, constructed using explicit solutions to the Laplace equation, which capture explicitly the behaviours of membranes in the splitting processes. The talk will be based on arxiv:1508.03367, done in collaboration with Stefano Kovacs (Dublin IAS) and Yuki Sato (Chulalongkorn Univ., Bangkok).