At this favored haunt of top models and stylists, white-smocked assistants can advise you on the relative merits of the incredibly effective and somewhat expensive skin lotions and hair potions, all packaged in disarmingly simple bottles. Happily, they also dole out generous take-home samples. An expansion in 2003 stretched the space to what was once known as Pear Tree Corner; in honor of the apothecary, the mayor had a new pear tree planted there. Subway: 4, 5, 6, L, N, R, Q, W to 14th St./Union Sq.