4. Remember Play-Doh?
Remember the smell of Play-Doh when you were a child? It instantly brings back memories. The brightly-coloured, nontoxic modeling clay was accidentally invented in 1955 by Joseph and Noah McVicker when they were trying to make wallpaper cleaner. A year later toy manufacturer, Rainbow Crafts, saw its true potential and marketed the product as Play-Doh.
More than 700 million pounds of Play-Doh have been sold since.