Fluorescence in situ hybridization (FISH) is a highly versatile laboratory technique combining the power of molecular analysis with details gained by fluorescence microscopy inspection at the single cell level. Initially introduced as a physical mapping technique for DNA sequence assembly at the time of the human genome project, FISH has re-invented itself repeatedly through time and, by doing so, succeeded in remaining at the forefront of research and diagnostic practice. In its various permutations FISH has been widely utilised for basic and applied research on genomes’ structural organisation, function and evolution. As a diagnostic technique, FISH is extensively used in clinical genetics and molecular pathology, and for single cell identification in microbiological analyses. This talk will provide an overview of modern FISH applications and ongoing developments, with particular focus on novel areas where FISH has joined forces with high-end technologies such as super-resolution microscopy and CRISPR. The role and relevance of FISH at a time when scientific advances appear to be increasingly driven by high-throughput approaches and ‘big data’ will be explored.