The goal of this study is to quantify and compare lung function in healthy controls and cystic fibrosis (CF) patients, with pulmonary function tests, multibreath washouts nitrogen (N2), and MRI studies. While current practices use pulmonary function tests (PFT) and forced expiratory volume (FEV1) to quantify lung ventilation in CF patients, multibreath washouts (MBW) and MRI studies are more sensitive to mucus build-up, lung function, and disease progression. By determining exactly where the excess mucus is and establishing correlations with lung function, we hope to provide the foundation for physicians to be able to customize treatment for individual CF patients.