Nipples don’t have muscle inside them — the erection of the nipple happens because of tiny smooth muscle fibers in the areola that contract in response to cold, touch, or sexual arousal.
The vagina lacks its own glands.
Unlike many organs, the vagina itself doesn’t have secretory glands—the moisture comes from cervical mucus and surrounding structures
Peak sexual encounters tend to cluster around night
A classic human behavior study found that, across adults, most sexual encounters occur around bedtime (roughly 11 PM–1 AM) — with a smaller peak after waking up.
