An illustration of a heliostat or a device that tracks the movement of the sun.

Heliostat

An illustration of a heliostat or a device that tracks the movement of the sun.

"Cross-sections of leaves of an oak (Quercus novimexicana), showing the effect of different light conditions on the internal anatomy. 1, from leaf growing in sunlight; 2, from leaf growing in the shade." -Gager, 1916

Oak Leaf Cross-Section

"Cross-sections of leaves of an oak (Quercus novimexicana), showing the effect of different light conditions…

A window with sunlight shining through.

Sunlit Window

A window with sunlight shining through.