Technology tree
From Kerbal Space Program Wiki
The tech tree is shown in the R&D center to unlock bigger, better and new parts as there is research done. As this is an initial release of this feature, new with version 0.22, this is subject to change. The tech tree shows all already developed researches and additionally shows the next researches available. The research of a node happen immediately and require a certain amount of science points which are collected through research.
The research Start is always researched when there is a new game started. The tech tree lists the research available at each step, and also the parts owned when completed. The following table contains all researches available: