Collections of natural materials—with their wide range of colors, shapes, and sizes—offer many opportunities for counting, sorting, grouping, and categorizing. Invite your child to start a collection of natural items like leaves, shells, or rocks, and then help him think about how to organize and display the items in his collection, using small trays or paper plates. Would he like to put all the big things together? All the small things? Maybe he would like to group the items by color or shape, or put items together based on where they came from? Remind him that he can organize the items in a different way on another day.