When a scientist makes a new molecule and has characterised it in a suitable manner, they would normally report on how it was made and perhaps on some aspect of its properties in a "Scientific Journal". This would then enable other scientists to repeat its preparation if they wished, and verify the assertions of the original scientist. Nowadays, many molecules are synthesised as part of a commercial activity. Sometimes, thousands of such molecules have to be made before one with suitable properties is finally found. Because all the information gathered about the molecules during the project can been very valuable commercially, the scientific world may never hear about them. Whilst it is difficult to estimate how many molecules have actually been made, but never reported, some estimates are of over 5 million.