Khat dealing at Tahrir Square, Sanaa, Yemen

Description: By 4 in the afternoon, most men walking the streets of Sana'a are high, or about to get high — not on any sort of manufactured narcotics, but on khat, a shrub whose young leaves contain a compound with effects similar to those of amphetamines. Khat is popular in many countries of the Arabian peninsula and the Horn of Africa, but in Yemen it's a full-blown national addiction. As much as 90% of men and 1 in 4 women in Yemen are estimated to chew the leaves, storing a wad in one cheek as the khat slowly breaks down into the saliva and enters the bloodstream. The newcomer to Yemen's ancient capital can't miss the spectacle of almost an entire adult population presenting cheeks bulging with cud, leaving behind green confetti of discarded leaves and branches.