Trisections Diagrams for Smooth 4-manifolds Abstract: A trisection of a smooth, compact, oriented 4-manifold X is a decomposition of X into three diffeomorphic codimension 0 submanifolds which have certain nice intersection properties. This decomposition, which is a 4-dimensional analog of Heegaard splittings of 3-manifolds, is known to exists for all smooth, compact 4-manifolds. There are