Regulation of protein adsorption and cell adhesion on surfaces is a key aspect in the field of biomedicine and tissue engineering. Beside the general studies on hydrophilic/hydrophobic surfaces, there are both fundamental and practical interests to extend the investigation of the interaction between proteins or cells and surfaces to the two extreme wettability ranges, namely superhydrophilicity and superhydrophobicity. This review gave an overview of recent studies on proteins or cells action on these two special wettability ranges. The first part will focus on the interaction between proteins and superhydrophilic/superhydrophobic surfaces. The second part will focus on cells adhesion on these extreme wettable surfaces. Surfaces can be patterned to control in space the wettability within extreme values. As an application of such substrates, flat chips for high-throughput screening are also addressed to offer new insight on the design of a new type of bioanalysis supports.