Jurors have been shown fragments of household items allegedly used by Salman Abedi in the homemade bomb which killed 22 and injured hundreds of others at the Manchester Arena in 2017.
Remnants of drinks cans, a paint tin and a novelty moneybox were all recovered from the scene of the blast as forensic officers scoured for clues in the aftermath of the disaster.
Tiny scraps of metal - some little more than 1mm in size - were found, along with nuts, screws and other items used to maximise carnage.
Abedi's brother, Hashem Abedi, is on trial at the Old Bailey accused of plotting the attack.
Lorna Philp, principal case officer with the Forensic Explosive Laboratory in Kent, told jurors many items recovered and processed by scientists were so small due to their proximity to the explosive, secreted in Salman Abedi's rucksack.
Giving evidence from the witness box, she said: "The damage to these fragments, the extremely small size, indicates these fragments were in close contact with the explosive itself when the device functioned."
She said shrapnel was also extensively damaged.
Ms Philp said her laboratory identified five different types of damaged and deformed nuts during the months-long forensic investigation into the bomb site.
The scientist also explained how components of homemade explosive TATP (also known as Tri-acetone Tri-peroxide) found at the scene could be made from readily available high street products.
Ms Philp described how analysis appeared to show the various components of the device, a replica of which was shown to jurors.
She said: "From the fragments covered, the device appeared to be constructed from a large money tin, a five-litre paint tin and an extremely large quantity of shrapnel, which consisted of nuts and screws."
Ms Philp said a green piece of material found at the scene was likely to be that of a boiler suit, probably placed in Salman Abedi's rucksack before he detonated the device.
The witness said: "It may have been in the rucksack either to disguise the shape of the tin, to hold the contents inside, or possibly cover the device if the bag was opened."
She added it was likely the explosion was triggered by a switch pressed by the perpetrator, "possibly (in) the jacket pocket".
Hashem Abedi denies 22 counts of murder, one count of attempted murder encompassing the injured survivors, and conspiring with his brother to cause explosions.
The trial continues.