Inside a lady

The female breast enlarges dramatically during sexual intercourse, increasing its size by up to 25%.

Blood is pumped into erectile tissues faster than it can be pumped away.

The nipples swell and become extra sensitive, increasing in height by as much as 1 cm.

The penis also becomes swollen and stiffly erect, doubling its normal length in the process.

The erect penis is a marvel of fluid mechanics.