A clear wine contains molecules, macromolecules and aggregates of molecules in solution, supersaturation or in stable or metastable dispersions. In the course of bottle storage, the formation of cloudiness and, subsequently, deposits is associated with phenomena of insolubilization and precipitation of molecules and/or aggregation between macromolecules and aggregates and subsequent flocculation. In this talk, the main causes of wine instability (tartaric, protein and colloidal) will be presented, and traditional, recently authorized and under study oenological practices to prevent cloudiness will be described. A particular focus will be on the role of polysaccharide additives on wine stabilization.