An assembly, in an example, may include at least one die, a substrate comprising at least one electrical trace, a lid coupled to a first side of the substrate to contain an amount of fluid between the substrate and lid, and an adhesive film coupled to a second side of the substrate to protect the at least one electrical trace wherein the lid further comprises a main chamber for each of at least two distinct fluids and an overflow chamber fluidically coupled to each of the main chambers via an overflow channel.