In initial reports from the July 7, 2005, bombings in London, police officials said the bombs' destructive power and small size meant they must have been made using high explosives, not a crude homemade concoction.

Soon, though, it became clear that they were homemade bombs, the explosive perhaps mixed in a bathtub and distilled in a kitchen, its chemical components available at the local pharmacist.

Chemists call it acetone peroxide, triacetone triperoxide (TATP) or tri-cyclo, but to Middle Eastern bomb makers, its power and unpredictability have earned it the nickname Mother of Satan.

Its ingredients are familiar, even to those who have never set foot in a chemistry lab.

Acetone: an industrial solvent and the main ingredient in nail polish remover.

Hydrogen peroxide: a common disinfectant and component in hair bleach.

Any strong acid, as a catalyst: sulphuric acid, hydrochloric acid.

Mixing these components in the right proportions under the right conditions will result in an explosive, triacetone triperoxide, or TATP. However, TATP is highly unstable and sensitive to heat. A bump can be enough to detonate it.

And because it's so unstable, TATP can't be stored for long periods of time. It degrades and evaporates in just a few days, becoming useless as an explosive. For this reason it is not used by military forces, but continues to be used in suicide bombings, such as the attacks on the London transit system this month.

Some have speculated that the TATP used in the July 7 and July 25 bombings of the London transit system may have come from the same batch, which would explain why the bombs on July 25 didn't go off.: the explosive degraded in the two weeks between the bombings.