They can look like a fish, a ball or a pen. Some are like butterflies, others like a toy windmill. But they are all deadly.
In a land where 10 million mines lurk beneath the soil and the surface is littered with unexploded ordnance, curiosity - especially children's curiosity - can kill.
"Some just look like a big nail," Ajmal Nassin, 21, a mine-awareness trainer, warns a class of 200 boys at Abum Qasim Ferduasi school, Kabul. "But don't touch them because they are connected to a wire that will explode when pulled. Sometimes even bank notes are wired up."
The school is situated in an area that has been on the frontline in numerous battles because a number of ministries are situated nearby. "If you step on one of these, you can die," Nassin says.
But even if you survive your life will never be the same. "If you don't have a hand you cannot work. If you don't have eyes you cannot see. If you don't have legs you cannot get to school."
Everywhere in Afghanistan you see adults on crutches with a leg or foot missing. But 85 per cent of victims of exploding ordnance are children. Many of them have triggered the explosion unwittingly as they hunt for scrap metal around military checkpoints.
They can earn $3 for seven kilos - good money in a country where teachers earn around $30 a month. But the risk they take is deadly.
So far aid agencies have been struggling against the tide to spread awareness as the numbers they can teach each week are outweighed by the thousands of refugees flooding back to the country.
One aid worker recalled with horror how her son once filled half a room with bullets and shells and came home carrying a rocket launcher on his shoulder.
Nassin, trained by Save the Children, visits 25 schools a week and has given demonstrations to 30,000 children in seven weeks. UNICEF introduced mine education into the training of all primary teachers this month and it will be checking that schools are including the topic in their curriculum.
What clues might children find that an object is a mine?
"If you see bones of dogs, or the clothes of a person lying around," said one boy in Nassin's class.
"If you see red warning stones or a flag," said another.
The children re-enact what to do if they find a suspect object. They approach a model bomb on the floor, stop, and retrace their steps in case there are others nearby. Then they leave a warning sign - a pile of stones or something red.
At that moment the sound of a large explosion interrupted the class. It is a mark of how much danger remains that de-miners are still trying to clear the area surrounding the runways at Kabul's international airport.