Littorina saxatilis is a model organism to study speciation in natural conditions. The most recent research points towards genomic inversions playing an important role in this process. Recently, we completed a high-contiguity assembly using Pacbio long read sequence data, HiC and Illumina short reads. This is currently being annotated. We have started to use this assembly in the analysis of both fine-scale (Koster region) and broad scale (North Atlantic) variation using WGS data (>400 individuals at 5-15x) This will help understand how the interplay between selective forces, neutral processes and chromosomal rearrangements could lead to speciation.