The human body is a machine whose many parts – from the microscopic details of our cells to our limbs, eyes, liver and brain – have been assembled in fits and starts over the four billion years of our ...

There are different reasons why one testicle may appear bigger than the other. If one of your testicles is slightly bigger than the other, don’t panic, this is completely normal for most men and boys.

If we look across the whole of the mammal branch of the tree of life, we find there are many groups of mammals that have ...

Dominant male lemurs flexibly grow their testicles when other males are around, putting them in a better position to successfully mate. In many species, dominant males have larger testes than ...

Undescended testicles (UT), which is used synonymously with the term cryptorchidism, is characterized as the failure of either one or both testes and their associated structures to descend during ...