One of my favorite types of photographs is a silhouette. Illumination for silhouetted scenes are provided by the background, throwing any foreground objects into shadow. The heavy shadows of the foreground objects, seen as black shapes with no inner details visible, juxtaposed on the brighter background that creates a beautiful contrast between light and dark.
My very favorite silhouette images are those taken outdoors just before sunrise or after sunset using the natural light from the sky for background (the sky doesn't have to be the background in every case). The contrast of darkened, pure forms against lighter twilight sky is absolutely gorgeous and if composed well produces some of the most elegant photographic scenes anywhere on Earth. I love them.
Here are five humble photographs featuring silhouettes I've taken I thought I'd share with you. Hope you enjoy them!

Twilight - 2003. Taken on transparency film (does anyone out there shoot slides anymore?)

Joshua Tree and Sunrise - 1994. Taken in the Mohave Desert, Nevada. I'd found this composition several months prior to actually shooting it so I could capture the sun rising right on that particular hillside in the background. Anal of me? Maybe so, yes I admit, and it took a fair amount of patience, but I was finally able to capture the scene just as I'd envisioned it.

Baton Rouge Sunrise - 2004. I'd planned to get the sun between the two taller buildings but I almost couldn't believe it when it rose perfectly right on top of the shorter building in the middle. That part wasn't planned, I was just lucky.

Joshua Tree and Twilight - 1995. I remember hiking a long way in the dark to photograph this scene at the right time.

Tao Mystery - 2006. This is one of my favorites. I love photographing on foggy days, it's great for shooting black and whites.