Here are some examples:
* "The tree is 30 feet in height." This means the tree measures 30 feet from the ground to its highest point.
* "She is 5'4" in height." This means she is 5 feet and 4 inches tall.
* "The building is impressive in height." This means the building is very tall.
Essentially, "in height" is used to express the vertical dimension of an object, much like "in length" is used for its horizontal dimension and "in width" for its side-to-side dimension.