Animal testing or animal research is the use of non-human
animals in scientific experimentation. It is estimated that 50
to 100 million vertebrate animals worldwide — from zebrafish to
non-human primates — are used annually. Although much larger
numbers of invertebrates are used and the use of flies and worms
as model organisms is very important, experiments on
invertebrates are largely unregulated and not included in
statistics. Most animals are euthanized after being used in an
experiment. Sources of laboratory animals vary between countries
and species; while most animals are purpose-bred, others may be
caught in the wild or supplied by dealers who obtain them from
auctions and pounds. The research is conducted inside
universities, medical schools, pharmaceutical companies, farms,
defense establishments, and commercial facilities that provide
animal-testing services to industry. It includes pure research
such as genetics, developmental biology, behavioural studies, as
well as applied research such as biome