Linker histones stabilize folded chromatin, acting through their long C-terminal tails. The C-termini contain high percentages of evenly distributed lysine and arginine residues and have no secondary structure in solution. Hence, it has generally been believed that the C-termini function by shielding negative charges on the DNA backbone. However, recent evidence supports a mechanism of action of the linker histone C-terminus that involves formation of specific secondary structure(s) upon interaction with other components of the chromatin fiber.