There's nothing in front of Ameur Saad's old house except for the Sahara.The world's largest hot desert stretches out endlessly before our eyes, a flattened expanse of granular white sand scattered with shrubs. Should you walk south in a straight line, you would eventually end up in Niger. The terrain would vary, but the essentials would remain the same: parched earth, granules between your teeth.For the moment, though, we're in Tunisia. It's dusk and the wind whips around us, throwing up the fine desert sand. Cotton scarves are wrapped around our faces, but the sand finds its way into our mouths and up our nostrils, sticking to every part of our body. Small mounds of it pile up at the corner of our eyes and in our pockets. It's not like beach sand, easily brushed off with a whack of a flip-flop. According to the Krumbein phi scale, a logarithmic scale that classifies particles, desert sand is categorized as "very fine sand."Here in Ameur's childhood village, known as Old Mahlel, it requires a Zen-like level of concentration to accept the grittiness.