[4] The initiative is projected to take 10 years (until 2021), and will focus on analysing homozygous mutant mice generated on an isogenic C57BL/6N background by the International Knockout Mouse Consortium.

The mouse strains are characterized in a broad based phenotyping pipeline that is focused on revealing insights into human disease by measuring embryonic, neuromuscular, sensory, cardiovascular, metabolic, respiratory, haematological, and neurological parameters.

The phenotypic data is recorded in a freely accessible, fully searchable online database,[8] generating what has been described as a "comprehensive encyclopaedia of mammalian gene function.

IMPReSS was launched in 2011 to help the IMPC achieve its goal of characterizing a knockout mouse strain for every gene and will continue to be actively developed for the ten year life-time of the project.

In 2013 the IMPC published the Bloomsbury report on mouse embryo phenotyping,[15] outlining a standard pipeline for the screening of embryonic-lethal knockouts in homozygote mutants.