The performance of biosensors can be adversely affected by the formation of small bubbles during their construction. In a cantilever-based biosensor molecules are immobilised on a gold surface, and the quality of the molecular layer influences the quality of the sensor. Scientists at the Technical University of Denmark in Lyngby report in Langmuir (2003, 19, 10510-10513) that nanobubbles with diameters of 50--130nm and heights of 0.4--6nm which are present on the gold surface can lead to an irregular molecular layer being formed, significantly influencing the performance of the sensor. Maria Holmberg and her team used a combination of contact-mode atomic force microscopy (AFM) and local force measurements to generate the first images of these nanobubbles and provide some detailed information on their characteristics. The nanobubble formation, when gold surfaces are exposed to clean water, is thought to be a general phenomenon and to be responsible for a number of artefacts in AFM images. The bubbles are found to maintain stable positions on the surfaces. The authors point out that this is difficult to understand as no underlying structures, which could immobilise the bubbles, can be identified on the gold surfaces.