Strained ring systems offer unique opportunities for C-C single bond activation. In this presentation, I will present three different fundamental approaches for ring-opening: heterolytic cleavage, single electron transfer and homolytic cleavage. Each strategy will be illustrated by one recent example from our research group: 1) Heterolytic cleavage: Silylium-catalyzed (4+2) annulation of indoles and aminocyclobutanes and application in the formal total synthesis of Strictamine (Angew. Chem.. Int. Ed. 2023, e202302420 and Helv. Chim. Acta. 2026, e202500163) 2) Single electron transfer: Oxidative ring opening of cyclopropanes using hypervalent iodine reagents (Chem. Sci. 2022, 12831 and JACS Au 2026, 10.1021/jacsau.5c01226) 3) Homolytic cleavage: Energy-transfer photocatalyzed ring opening reactions of cyclopropanes (JACS 2023, 25411 and Angew. Chem., Int. Ed. 2024, e202417719)