From the book The Machinery of Life by David S. Goodsell. You can read about the artist's process here.
This is an illustration of the first stage of the central dogma of molecular biology, often stated simplistically as "DNA makes RNA, and RNA makes protein". Our DNA stores the blueprints for the unimaginably vast array of self-assembling nanomachines that make our body work, which are called proteins. Once a protein is made, it does not propagate any information back to DNA; DNA alone encodes the genome. However, it is possible for RNA to modify DNA. This is how HIV installs itself as a rootkit in the cell, which will be covered in a future post.
The nucleus is the cell's library, storing the delicate strands of DNA and protecting them from the rigors of the cytoplasm. Much of the DNA is wrapped around histone proteins to form small nucleosomes (yellow four-legged proteins) that compact and protect the DNA. When the DNA is needed, it is unwrapped, unwound, and read by RNA polymerase (large orange protein engulfing the yellow strand) to create a messenger RNA (thin purple rope). The RNA molecules are then processed: capping enzymes protect one end and polyadenylate polymerase adds a repeated string of adenine nucleotides to the other end, which are then protected by the polyadenylate binding protein. Our RNA must also be edited by large splicosome complexes (large light purple protein) to remove intron regions that do not encode proteins. Once the RNA is properly edited, it is delivered out of the nucleus through nuclear pore complexes (large green structure). These pores span the double-layered nuclear membrane and control the traffic of a diverse collection of importin proteins (purple protein traversing the large green structure), which carry other molecules in and out. The nuclear membrane is strengthened inside by criss-crossed layers of lamin protein filaments (in blue) (1,000,000 X)
Here is the zoomed-out context for this illustration; it shows the leftmost part of the rectangular colored box in this human blood plasma cell (10,000 X):
Future posts will move from left to right along this cross section, following the stages of the central dogma.
The nucleus is the library of the cell.