The present application relates to methods for identification of foetal cells and generation and isolation of binding members recognising foetal cells. Said methods may further be used for other purposes relating to characterisation of biological samples and biological antigens. The methods are characterised by the applicability in situations where the interesting objects are present in a limited amount, or where the interesting objects are intermixed with other material, thus the methods are suitable for use in situations where the ratio of the interesting material compared to other material is low. The application discloses methods for use of detecting foetal cells and method of generating/isolating binding members towards antigenic material of low abundancy.