A key feature of myotonic dystrophy type 1 (DM1) and 2 (DM2), is the accumulation of RNA-protein aggregates, primarly in cell nuclei. However, unravelling their structure, dynamics, and function remains a challenge. To resolve RNA foci ultrastructure, we introduced Expansion Microscopy (ExM) as an innovative approach to DM research. The combination of ExM with other techniques, such as single-molecule inexpensive FISH (smiFISH), provides another approach to high-resolution visualization of MBNL-C(C)UG repeat transcript complexes in cell types relevant to DM pathology.