Wood!
These four logs are found throughout the minecraft world. On the top left we have the very first wood added. This wood is oak, and is the first wood put into minecraft. On the top right we have the second wood added, which is birch. The third, added in beta v 1.8.1 is spruce. And the final wood, jungle was added in full v 1.0.0. the colors of the wood planks were added in full v 1.2.3/1.2.5. The ability to place the logs sideways was added in full v 1.3.2. Two new types of wood have been added since then. They are Acacia and Dark Oak. Acacia is an orange colored wood and Dark Oak is a very dark brown color (Darker than spruce!)