The paper discusses the role of nanoscale phase separation in colossal magnetoresistance (CMR) materials, particularly manganites, and its implications for high-temperature superconductors (cuprates). It highlights that the CMR effect in manganites arises from the competition between ferromagnetic metallic and charge-ordered insulating phases, leading to inhomogeneous states. These inhomogeneities are observed in both manganites and cuprates, with similar phenomenology. Theoretical models suggest that phase competition in manganites can be analogous to that in cuprates, where competing phases such as antiferromagnetic and superconducting states may coexist. The paper proposes that the pseudogap temperature $ T^* $ in cuprates could correspond to a Griffiths temperature, where clusters begin to form upon cooling. It also suggests that quenched disorder may play a more significant role in cuprates than previously thought. The paper reviews experimental and theoretical evidence for phase competition in manganites, including the presence of inhomogeneities, charge ordering, and spin-glass behavior. It discusses the implications of these findings for cuprates, including the possibility of a spin-glass regime as a mixture of antiferromagnetic and superconducting islands, and the prediction of "colossal" effects in cuprates. The paper also explores the role of disorder in cuprates, suggesting that it may be more important than previously anticipated. It concludes that the general principles of phase competition in manganites may apply to cuprates, leading to similar phenomenology and potentially important speculations about their behavior. The paper emphasizes the importance of understanding phase competition and inhomogeneities in both manganites and cuprates to better understand their properties and behavior.The paper discusses the role of nanoscale phase separation in colossal magnetoresistance (CMR) materials, particularly manganites, and its implications for high-temperature superconductors (cuprates). It highlights that the CMR effect in manganites arises from the competition between ferromagnetic metallic and charge-ordered insulating phases, leading to inhomogeneous states. These inhomogeneities are observed in both manganites and cuprates, with similar phenomenology. Theoretical models suggest that phase competition in manganites can be analogous to that in cuprates, where competing phases such as antiferromagnetic and superconducting states may coexist. The paper proposes that the pseudogap temperature $ T^* $ in cuprates could correspond to a Griffiths temperature, where clusters begin to form upon cooling. It also suggests that quenched disorder may play a more significant role in cuprates than previously thought. The paper reviews experimental and theoretical evidence for phase competition in manganites, including the presence of inhomogeneities, charge ordering, and spin-glass behavior. It discusses the implications of these findings for cuprates, including the possibility of a spin-glass regime as a mixture of antiferromagnetic and superconducting islands, and the prediction of "colossal" effects in cuprates. The paper also explores the role of disorder in cuprates, suggesting that it may be more important than previously anticipated. It concludes that the general principles of phase competition in manganites may apply to cuprates, leading to similar phenomenology and potentially important speculations about their behavior. The paper emphasizes the importance of understanding phase competition and inhomogeneities in both manganites and cuprates to better understand their properties and behavior.