Large scale models of natural phenomena are one of the most challenging classes of problems in science and computing. Galaxy and star formation models are one type; weather and climate are another important area of modeling. The models themselves are vastly complex, encompassing a huge number of variables, and necessitating difficult decisions about setting initial conditions, tuning assumptions in the model, and matching the scale and granularity of the model to the hypothesis being investigated. It’s tiring just considering the size of the challenge. Scientists are expressing new optimism about galaxy simulation models. While early models didn’t produce results that matched observation, more recent models are corresponding better to observations and increasing scientists’ confidence that they models can begin to serve in a predictive role and lead to new discoveries in cosmology.