Tricky question but I will have a go!
As Kristi says, people often begin to notice sexual feelings and needs when they reach puberty and begin to produce sex hormones like oestrogens and testosterone.
Did you know that this is controlled by the brain? A bit of brain called the hypothalamus starts to produce a hormone called Gonadotrophin Releasing Hormone at puberty in both boys and girls. It’s such a mouthful we shorten it to GnRH but it’s job is to stimulate ovaries and testes to make the sex hormones.
But sexual needs is about more than just biological needs for passing on genes and release of tension and yes, this is also linked to hormones. an important one is sometimes called ” the love hormone” and it’s name is oxytocin. In the past people thought it was only made by women, but now we know that it’s important for social bonding making relationships and having feelings of love, belonging and security.