L-Homoserine lactones comprise a family of mediators of cell to cell interactions between bacteria, notably in bacterial biofilms. When secreted by the producing bacteria, homoserine lactones modulate a diverse range of metabolic functions in surrounding species, regulating not only growth and motility but also the production of secondary metabolites such as antibiotics. The most significant variable defining the function of the homoserine lactones is the length of the acyl chain, with shorter chains displaying opposing actions to the longer chains. The L-Homoserine Lactone Analogue Set provides the full set of available homoserine lactones from acetyl (C2) to octadecanoyl (C18).