Pattern formation is a frequent phenomenon in physics, chemistry, biology and material science. Bottom-up pattern formation occurs usually in the interaction of the transport phenomena of chemical species with their chemical reaction. The oldest pattern formation is the Liesegang phenomenon (or periodic precipitation), which was discovered and described by Raphael Edward Liesegang in 1896, who was a German chemist and photographer, and he was born 150 years ago. The purpose of this review is to provide a comprehensive overview of this type of pattern formation. Liesegang banding occurs due to the coupling of the diffusion process of the reagents to their chemical reactions in solid hydrogels. We will discuss several phenomena observed and discovered in the past century including reverse patterns, precipitation patterns with dissolution (due to complex formation), helicoidal patterns, and precipitation waves. Additionally, we will review all existing models of the Liesegang phenomenon including pre- and post-nucleation scenarios. Finally, we will highlight several applications of periodic precipitation.

4‐Hydroxynonenal (HNE) is an important product of plasma membrane lipid peroxidation, which is a cause of cell and tissue injury. Mitochondrial DNA (mtDNA)‐depleted ρ⁰ cells were established using human cervical cancer and oral squamous cell carcinoma cell lines. We investigated the effect of reactive oxygen species in ρ⁰ cells, especially the mechanism of hydrogen peroxide (H₂O₂)‐mediated cell death. These cell were subjected to high oxidative stress and, compared with their parental cells, showed greater sensitivity to H₂O₂ and high lipid peroxidation. Upregulation of HNE in the plasma membrane was observed prior to the increase in intracellular H₂O₂. The amount of oxidized lipid present changed H₂O₂ permeability and administration of oxidized lipid led to further cell death after treatment with H₂O₂. Expression levels of lipoxygenase ALOX genes (ie ALOX5, ALOX12, and ALOX15) were upregulated in ρ⁰ cells, as were expression levels of ALOX12 and ALOX15 proteins. ALOX5 protein was mainly distributed in the nucleus, while ALOX12 and ALOX15 proteins were distributed in the nucleus and the cytoplasm. Although expression of COX2 gene was upregulated, its protein expression did not increase. ALOX (especially ALOX15) may be involved in the sensitivity of cancer cells to treatment. These data offer promise for the development of novel anticancer agents by altering the oxidation state of the plasma membrane. Our results showed that lipid peroxidation status is important for H₂O₂ sensitivity and that ALOX15 is involved in lipid peroxidation status.