This is the third dataset associated with the updated manuscript on mtFociCounter. Images are Spinning Disk Confocal Images of unsorted 3t3 NIH mouse fibroblasts stably expressing mitochondrially targeted dsRed, immunofluorescence against dsDNA (mitochondrial nucleoids) and AlexaFluor 647, and nuclei stained with Hoechst. Together with dataset_01, it contains all data necessary to reproduce the analysis of 3t3 WT cells, as described in the manuscript. "samples" from the same day are 13mm coverslips processed in parallel (seeding of cells, fixation, immunofluorescence and imaging) and mounted on the same glass slide (#1 on left, #2 centre, #3 right), whereas different dates can be considered biological replicates, of which there are 19 in total (with dataset 01). Please beware, there is some redundancy with dataset_02, and we recommend combining dataset_01 with dataset_03 for further analysis. This dataset_03 contains the 3t3 WT data from the following acquisition dates: 20221025_sample1 20221026_sample2 20221029_sample1 20221029_sample2 20221110_sample2 20221210_sample1 20221211_sample3 20221212_sample3 20221217_sample2 20221220_sample2 20221221_sample3 For further details on the experimental procedure, please refer to the accompanying manuscript, which will soon be made available on BioRxiv.