solutal Marangoni flows occurring during evaporation. Mixtures of low boiling point and high boiling point solvents were shown to suppress the coffee ring effect, changing the shape of a deposited solute from a ring-like to a dot-like shape. Control of the substrate temperature was shown to be an effective way to suppress the coffee ring formed by droplets of water-based PEDOT:PSS solution. On a heated hydrophilic or hydrophobic substrate, a thinner ring with an inner deposit forms, which is attributed to Marangoni convection. Control of the substrate wetting properties on slippery surfaces can prevent the pinning of the drop contact line, which will, therefore, suppress the coffee ring effect by reducing the number of particles deposited at the contact line. Drops on superhydrophobic or liquid impregnated surfaces are less likely to have a pinned contact line and will suppress ring formation. Drops with an oil ring formed at the drop contact line have high mobility and can avoid the ring formation on hydrophobic surfaces. Alternating voltage electrowetting may suppress coffee stains without the need to add surface-active materials. Reverse particle motion may also reduce the coffee-ring effect because of the capillary force near the contact line. The reversal takes place when the capillary force prevails over the outward coffee-ring flow by the geometric constraints. Determinants of size and pattern The lower-limit size of a coffee ring depends on the time scale competition between the liquid evaporation and the movement of suspended particles. When the liquid evaporates much faster than the particle movement near a three-phase contact line, coffee ring cannot be formed successfully. Instead, these particles will disperse uniformly on a surface upon complete liquid evaporation. For suspended particles of size 100 nm, the minimum diameter of the coffee ring structure is found to be 10 μm, or about 10 times smaller than the width of human hair. The shape of particles in the liquid is responsible for coffee ring effect. On porous substrates, the competition among infiltration, particle motion and evaporation of the solvent governs the final deposition morphology. The pH of the solution of the drop influences the final deposit pattern. The transition between these patterns is explained by considering how DLVO interactions such as the electrostatic and Van der Waals forces modify the particle deposition process. Applications The coffee ring effect is utilized in convective deposition by researchers wanting to order particles on a substrate using capillary-driven