A construction, comprising: a first memory array deck; and a second memory array deck over the first memory array deck; wherein the first and second memory array decks comprise phase change memory, and wherein the second memory array deck differs from the first memory array deck in one or more operating characteristics; wherein: memory cells of the first memory array deck are laterally spaced from one another by first dielectric regions along a cross-section; and memory cells of the second memory array deck are laterally spaced from one another by second dielectric regions along the cross-section; characterised in that: the first dielectric regions comprise first insulative material liners along sidewalls of memory cells and a first insulator between the first insulative material liners; the second dielectric regions comprise second insulative material liners along sidewalls of memory cells and a second insulator between the second insulative material liners; and the first dielectric regions differ from the second dielectric regions in one or more structural parameters including at least one of: differing composition of first and second insulator materials; and differing composition of first and second insulative material liners. a first memory array deck; and a second memory array deck over the first memory array deck; wherein the first and second memory array decks comprise phase change memory, and wherein the second memory array deck differs from the first memory array deck in one or more operating characteristics; wherein: memory cells of the first memory array deck are laterally spaced from one another by first dielectric regions along a cross-section; and memory cells of the second memory array deck are laterally spaced from one another by second dielectric regions along the cross-section; characterised in that: the first dielectric regions comprise first insulative material liners along sidewalls of memory cells and a first insulator between the first insulative material liners; the second dielectric regions comprise second insulative material liners along sidewalls of memory cells and a second insulator between the second insulative material liners; and the first dielectric regions differ from the second dielectric regions in one or more structural parameters including at least one of: differing composition of first and second insulator materials; and differing composition of first and second insulative material liners. memory cells of the first memory array deck are laterally spaced from one another by first dielectric regions along a cross-section; and memory cells of the second memory array deck are laterally spaced from one another by second dielectric regions along the cross-section; characterised in that: the first dielectric regions comprise first insulative material liners along sidewalls of memory cells and a first insulator between the first insulative material liners; the second dielectric regions comprise second insulative material liners along sidewalls of memory cells and a second insulator between the second insulative material liners; and the first dielectric regions differ from the second dielectric regions in one or more structural parameters including at least one of: differing composition of first and second insulator materials; and differing composition of first and second insulative material liners. the first dielectric regions comprise first insulative material liners along sidewalls of memory cells and a first insulator between the first insulative material liners; the second dielectric regions comprise second insulative material liners along sidewalls of memory cells and a second insulator between the second insulative material liners; and the first dielectric regions differ from the second dielectric regions in one or more structural parameters including at least one of: differing composition of first and second insulator materials; and differing composition of first and second insulative material liners.