TIP n.1THE SLOW ONES FIRST It is much more easier to complete a level when you bring the Blue Molecules first to one side, and only then you start managing the Red Molecules.
TIP n.2 WALL CONTROL You may find useful to change the wall control to "Push = Off". This is mostly valid when the number of molecules is high. Go to the Option screen to change the behavior of the wall button.
TIP n.3RESTART LEVEL Rarely can happen that the molecules have some sort of synchronization so that it is very hard to manage them. In that case just try to restart the level (click the pause button and then the "reload" button).
TIP n.4PARADIGM SHIFT (This considers you are applying TIP n.1) Sometimes, when you are stuck with just a couple of blue molecules and cannot find a way to bring them over, you may try to open the wall and let the whole block of blue molecules run on the opposite side. This creates a sort of partial reshuffle. As strange as this may seem, this maneuver often works great. For experts only!