Eukaryotic cells have a number of intracellular organelles with distinct functions. Interestingly enough, these organelles never function alone; they cooperatively regulate cellular homeostasis, proliferation, and differentiation, through a continuous exchange of soluble and membrane-bound molecules via membrane trafficking and/or membrane contact transfer. A failure in organelle cooperation often results in various human diseases. Our laboratory uses methods in biochemistry, cell biology, and molecular biology to identify novel organellar proteins and lipids. With these methods, we aim to unveil novel functions of organelles and the molecular mechanisms that regulate organelle cooperation. We especially focus on molecules that reside on the cytoplasmic face of the organelles; the essential face that physically interacts with other organelles and cytosol. Our results will help develop new treatments for diseases such as cancer and autoinflammatory diseases that are caused by disrupted organelle cooperation.