Cells produce many different complexes. These complexes can occupy 40% of the cell's volume, making the cell quite a crowded environment. For that reason, a full description of complex cellular behavior is a challenge that requires deeper investigation. To mimic the crowded nature of the cell, researchers usually apply chemically inert molecules, like non-ionic polymers, making solutions that work as obstacles for biologically active molecules while reacting. However, these inert compounds are not as inert as they should be. As it turns out, they tend to "steal" ions and that was quite a problem for the researchers. Even a minor change of the ions concentration in the cell can dramatically affect biochemical reactions. Recently, scientists from the Institute of Physical Chemistry, Polish Academy of Sciences, led by prof. Robert Holyst, presented research that brings us closer to understanding up to 1000-fold changes in the equilibrium constants of biochemical complex formation occurring in very crowded environment.