Molecular chaperones and chemical compounds like amino acids and osmolytes share the capability to prevent protein aggregation and can contribute to rescue in vivo aggregated proteins. Therefore, both overexpression of the molecular folding machinery and induced accumulation of chemical chaperones are options to improve the correct folding of recombinantly expressed proteins. These two parameters may show synergistic effects, although success remains protein specific and, therefore, several combinations of molecular and chemical chaperones should be compared. However, proteins can fail to fold correctly even in optimized culture conditions. In this case, protein aggregates can be recovered and their refolding assisted by an osmolyte/chaperone-dependent system. The selection of aggregates with different degrees of complexity can be exploited to maximize the yields of native proteins at the end of the refolding process.