Do organs always have more than one type of tissue within them?

As you may already know, every part of your body is made of tissues, as tissues are defined as a group of cells performing similar or same functions. So not only is skin tissue, but semen and blood is as well.

Now, back to your question. When we are formed, the cell that you are first conceived as splits itself into things called "Stem cells." You may have heard of these on the news, as the research using them is very controversial. The reason why is simply because the only way to get at them is to kill what has the potential to become a human baby.

But I digress again. These stem cells are so important and are being researched because they have the potential to turn into any bodily cell. Any of them. A blood cell, a liver cell, a skin cell, anything.

So to answer your question, no. Organs are specialized for what they do, and are not made up of the same tissues.