Immunosignal hybridization chain reaction (isHCR) combines antibody-antigen interactions with hybridization chain reaction (HCR) technology, which results in amplification of immunofluorescence signals by up to two to three orders of magnitude with low background. isHCR's highly modular and easily adaptable design enables the technique to be applied broadly, and we further optimized its use in multiplexed imaging and in state-of-the-art tissue expansion and clearing techniques.