The O’Porto Blood Bank is built on a detached plot with an irregular polygon in the heart of a city block. The building-as-line runs through the polygon´s different directions searching its geometry. The Blood bank supports all activities of regional blood collection and analysis as well as its partition in 3 components (erythrocytes, plasma and platelets). These components are later to be distributed to hospitals and pharmaceutical industries. This typology is new and hardly tested. It has a great complexity due to permanent risk of blood contamination. Continuous scientific and technological developments force permanent alterations. It is therefore a building with an unstable interior, which will undergo frequent metamorphosis throughout its life. The building program is a linear sequential process (of blood disassembly). It suggests to be more adequate a low and fluid construction rather than a high building, as pointed out by the neighbouring housing buildings (5 and 6 levels).