The process through which disordered components spontaneously arrange themselves into patterns is called self-assembly. Molecular self-assembly describes the process by which molecules adopt a defined arrangement without external guidance (e.g. formation of membranes and protein complexes). These biological processes are essential to the functioning of cells. We investigate the usage of BlenX, a process calculi based programming language, for modelling molecular self-assembly of filaments, trees and rings. Moreover, we show how these structures can be used to model actin polymerization.