Starting with newborns, the Perfect Cup has managed to find something with a coffee ot tea theme for every age. A children's corner, overseen by a life-size clown, has cups and soda mugs, bibs and animal bean bags, and a line of children's teas that are caffein-free and scented with herbs and spices. The rest of the store features twenty-six kinds of coffee (most from $6.35 to $6.99 a pound) including authentic Blue Mountain (at a whopping $10.95 a pound and limited to one pound per sustomer). There are about a hundred different herbs in bulk, which they will sell in quantities as small as one ounce. It has thirty-eight herbal and regular teas, all in vividly capped apothecary jars. To serve with its beverages, the Perfect Cup sells dried fruits, most of them sugar-free; freshly ground peanut butter, honeys and French jellies; and imported candies. For brewing and serving, there is a case full of antique coffee and chocolate pots and cups, comtemporary mugs and coffeemakers. The shop has handmade sachets for the herbs, gift packages filled to order, and a lime of original coffee-oriented greeting cards to accompany the gifts. Perhaps most important, the Perfect Cup has a cafe to serve the coffee and tea of your choice, brewed to order, along with pastries, yogurt and sherbet. If you like what you find at the perfect Cup, look into its coffee and tea club. For $7.50 a year membership you get six newsletters a year with recipies and shopping tips and news of special members' discounts, and everthing you buy is discounted five per cent; plus a record of your preferences kept on file in case anything wants to choose a gift for you.

The Perfect Cup, Rialto in White Flint Mall, Rockville. open Monday through Saturday, 10 a.m. to 9:30 p.m. 770-6333.