Note that this is just a rough estimate, without considering the distribution of the organic contaminants between dissolution and interface adsorption (one side is the atmosphere). If the distribution is taken into account, the concentration of stable bulk nanobubbles would decrease. This is also consistent with the experimental observations that the concentration of bulk nanobubbles can be substantially reduced if the solution is carefully prepared to remove the organic contaminants. However, the organic contaminants in solution itself are not the single source of amphiphilic molecules. Organic contamination may also come from other sources. For example, the solution surface and the container exposure to airborne contaminants, both may introduce contaminants. Several reports showed that graphite surfaces exposed to air may accumulate a thin organic layer. With the compressed amphiphile monolayer, we can predict the ubiquitous existence of bulk nanobubbles in aqueous solution, with a more or less bubble concentration. This ubiquity is based on the following facts: unavoidable existence of trace organic contaminants that act as a source of amphiphiles, and the interface adsorption of amphiphiles and shrinking of large bubbles that leads to the formation of compressed amphiphile monolayer, and the bulk nanobubbles with such a monolayer are thermodynamically stable. Therefore, we can safely conclude that the appearance of bulk nanobubbles can be much more commonly found than we expected.