Membranes fascinate me for two reasons: Their role as building blocks of life and their exotic mechanical properties. We can argue that membranes are the most important constituents of living cells, because no life on earth exists and none is conveivable without membranes, making membranes the most plausible candidates for the first step in the origin of life. The unique mechanics is that of a liquid forming robust thin layers, elastic against bending while fluid against other changes of shape.

Membranes are required for most of life's energy generation. Each living being employs one or more of the following methods to obtain energy: respiration, photosynthesis, fermentation and various kinds of chemosynthesis. With the exception of fermentation, all of these methods are based on a proton gradient across a membrane, built up and harvested by proteins embedded in the membrane. It is even plausible that first living being needed to have a membrane-based metabolism.

Membranes divide the inside of the cell from the environment and therefore are the place where exchange between a cell and the rest of the world happens. Cells are either prokariotes or eukariotes, the only prokariotes being archaea and bacteria. All eukariotes are divided by membranes into various organelles, including a nucleus. A network of pathways connect the organelles and the exterior world, and along those paths in both directions, a steady traffic of materials is carried in membrane vesicles, which bud off from the membrane of the origin, get dragged along the path and fuse with the membrane at the destination. Under certain conditions, an entire organelle can be broken down into vesicles, which can then fuse again to rebuild it.

The names prokariote and eukariote mean "before nucleus" and "true nucleus" respectively, because the characteristic of the eurkariotes is to have an organelle called the nucleus, which stores most of the genes. The nucleus is wrapped in the nuclear envelope, which consists of two layers of membrane perforated by nuclear pores, which are short tubules connecting the two layers, enclosing a volume between the two membranes. However, the nucleus is not the only organelle characteristic for eukariotes. One of the others is a complicated structure of membranes called the endoplasmic reticulum (ER), which attaches to the nucleaus, continuing both volume und surface of the nuclear envelope. The ER is a network of sheets and tethers and one exciting question is how such a structure is formed and maintained.