The hamster egg penetration test (HEPT) (also known as the sperm penetration assay) is the most accurate test that predicts whether your sperm will be able to fertilize an egg. It can also predict whether lab techniques can improve your sperm’s ability to fertilize an egg.

During a hamster egg penetration test, a lab analyst will evaluate your sperm samples using techniques that are similar to the techniques used in IVF. The only difference is that a doctor uses eggs from a hamster. A lab analyst will chemically treat hamster eggs to see if human sperm can penetrate them.

The prepared sperm are incubated with 15 to 20 chemically treated eggs. If your sperm is working how it should, it will be able to penetrating the eggs. The lab analyst will then count how many eggs were penetrated and calculate a percentage.

Although medical professionals often present the procedure as unable to create an embryo, these claims are not technically correct. If the human sperm succeeds in penetrating the hamster egg, a hybrid embryo is indeed created, known as a humster. These embryos are typically destroyed before they divide into two cells; were they left alone to divide, they would still be unviable.

Prof Stephen Wallace from the University of Edinburgh is among those turning the fatbergs into perfumes. "It's a crazy idea," he admits to me, "but it works."
Fatbergs are accumulated lumps of fat from cooking oils, toilet and other food waste that people put down their drains. Prof Wallace gets his from a company that specialises in fishing them out of sewers and turning them into biofuels. They arrive at the lab in a tube.
The first step is to sterilise the material in a steamer. Prof Wallace then adds the specially modified bacteria to the remnants of the fatberg. The bacteria have a short section of DNA inserted, to give the bacteria their particular properties.
The fatberg gradually disappears, as the bacteria eat it, producing the chemical with the pine-like smell - this can be used as an ingredient in perfumes.