Thymus function (100X)

Functionally, the thymus ensures T-cells can recognize self-MHC molecules (positive selection) and won’t attack the body’s own tissues (negative selection). Only about 2% of T-cells pass this gauntlet, making the thymus a ruthless quality-control manager. While the thymus is s a star player in early life, it starts shrinking after puberty. Look at the adult thymus for comparison and see the decay for yourself.

Here you can see the medulla and cortex at 10X magnification. Magnify for further detail.