Certain items can be researched and improved but do not appear on the tech tree. They are usually unlocked for construction from the start of the Missions, although occasionally they must be unlocked with Technology crates or research of a Traded item. Improvements reduce the cost to manufacture these items in a Factory as with items on the tech tree.
Each build-able/buy-able item on the research tree can be researched up to nine times. This is referred to as 'improving' it in-game. This decreases the amount of time and Energy each item takes to create in the Factory by 5% per level. You can chose to research items manually, by placing it on the Analyser, or let the Researchers do it automatically when they have nothing else to do. You do not get to chose which items are 'improved' when automatic research occurs, they are researched in whatever order the Laboratory decides. After researching an item nine times, additional items placed on the Analyser will simply vanish.
Bombs and Artwork placed on the Analyser will just vanish, Corpses will produce an autopsy report.
Food Supplies and Mineral Ores cannot be created by your Factories, but can be researched. The purpose of 'improving' these items is unclear.
Turdite can be researched, as well as Plants and Litter. It has been suggested that this research increases their recycle value. Although there is no official confirmation of this, the 'improved' message will still appear, suggesting something has been changed.
Plant research was suggested to be increasing their growth rate/reappearance rate on BioDeck but there's no widespread confirmation.