Detection of trace numbers of cancer cells is crucial for the recovery of the patients who have undergone drastic chemo or radio therapies. Attempting to diagnose complex cancer phenotypes clinicians face multiple problems, e.g.: the heterogeneity of cancer entities, the plasticity of the genotypes and phenotypes of cancer cells, and the low number of cancer cells relative to the normal cells in post-therapy samples. These problems are approached by molecular genetics studies, molecular biomarkers, imaging and importantly, the development of new devices suited to perform accurate, high-throughput quantitative and qualitative analysis of specimens. Interdisciplinary collaborations and the fusion of basic and applied research aimed towards advancing innovation have led to valuable improvements for clinical diagnostics. This paper highlights current advances in developing microfluidic devices for single cell or small sample analysis in biomedicine.