The core histone tail domains play important roles in different stages of chromatin condensation. The tails are required for folding nucleosome arrays into secondary chromatin structures such as the ∼30 nm diameter chromatin fiber and for mediating fiber–fiber interactions important for formation of tertiary chromatin structures. Crosslinking studies have demonstrated that inter-nucleosomal tail–DNA contacts appear in conjunction with salt-induced folding of nucleosome arrays into in higher order chromatin structures. However, since both folding of nucleosome arrays and fiber-fiber interactions take place simultaneously in >2–3 mM MgCl 2 such inter-nucleosome interactions may reflect short range (intra-array) or longer range (inter-array) interactions. Here, we describe a novel technique to specifically identify inter-array interactions mediated by the histone tail domains. In addition, we describe a new method for the preparation of H3/H4 tetramers.