Retina

The human retina contains six different layers that include bipolar and rod cell photoreceptors, horizontal and bipolar cells, and ganglion cell neurons. These layers are complicated and full of lots of other neuronal subtypes such as interneurons. When sectioned the retina looks like a bizarre layer cake. Ramon y Cajal won the Nobel Prize in 1906 for his imaging of the retinal layers.

Santiago Ramón y Cajal developed a method of staining neurons with silver nitrate that allowed neuronal cell anatomy to be visible.  He hand drew what he saw, and the beauty of his drawings is breathtaking.

Hearts

The human heart weighs less than a pound.  It’s beat is rhythmically controlled by sympathetic and parasympathetic neurons that are instantaneously responding to the bodies needs and emotional states.  Heart disease is the leading cause of death in the world.

Lungs

Stomaches