Metal oxides are an important class of materials as most metals spontaneously develop an oxide layer in ambient conditions. These materials are not only abundant, but also offer a wide range of interesting properties. A prototypical example is titanium dioxide (TiO2), which is utilized in many industrial applications such as in photocatalysis, dye-sensitized solar cells, and heterogeneous catalysis. At present, the surfaces of TiO2 are well understood under highly idealized ultrahigh vacuum (UHV) conditions. In reality, however, surfaces are surrounded by gases and covered with liquids. Many practical processes involve a solid surface immersed in an aqueous solution. In air, surfaces are automatically covered by a thin film of condensed water. It is often the solid-liquid interface that defines the performance of a material in application. Understanding atomic scale processes closer to real conditions is essential for a rational design of materials, and further improvement and increased efficiency in applications. The investigation of surfaces under ambient conditions remains a challenge due to the restricted number of available experimental techniques and a high chance of contamination. We have designed an experimental apparatus that allows dosing ultrapure liquid water on the surface of a sample (typically a single crystal) without exposure to air. The apparatus is coupled to an existing surface-science chamber, which enables reproducible sample preparation and sample characterization by UHV-based analytical techniques. Within the thesis, the interaction of liquid water with the two lowest-energy terminations of TiO2 rutile was studied. The (110) surface was found to retain its bulkterminated (11) structure upon immersion in pure liquid water. In addition, we clarified the origin of a molecularly ordered overlayer previously reported by several research groups. This overlayer consists of a mixture of carboxylates, and, upon exposure to air, spontaneously forms on the surface. Despite their relatively low atmospheric concentration, carboxylic acids adsorb on TiO2(110) with a high affinity and block the undercoordinated surface cation sites. In contrast, the (011) termination of TiO2 rutile was identified to change its surface structure upon contact with liquid water. As predicted by DFT calculations, the original (2 1) reconstruction was lifted, and dissociated water remained on the unreconstructed (11) surface in the form of an ordered (21) overlayer. Apart from detailed experimental results, the thesis also covers the design of the UHV-compatible apparatus for dosing pure liquid water, a brief description of the used techniques and a short introduction into the investigated surfaces.