The prettiest, most grown-up bed I've ever slept in was a twin. I was 21 and not really a pink person, but I loved that bed upholstered in a rich rose linen. While twin beds otherwise make me think of little kids, the moral of the pink bed story is that a well-styled twin can maximize space without looking juvenile.
MORE TWIN BEDS ON APARTMENT THERAPY:
(Images: 1. Vintage House 2. Loft & Cottage 3. Two Ellie 4. Barry Calhoun for Style at Home magazine via Poppytalk 5. Haven in Paris via A Cup of Jo 6. Little Fine Day 7. Gregory Han for Apartment Therapy 8. Scuba's Open House)