Which cell organelle controls most of the activities of the cell?

Hint: If a cell organelle has to control most of the functions, it should be conspicuous and principal organelle. It should also contain important information molecules like DNA.

Complete answer:
We all have come across different organelles but the one that does multi-tasking is Nucleus. It is a double-membrane, specialized structure that bounds genetic material known as DNA.
The credit for this discovery goes to Robert Brown in 1831. The role of nucleus in heredity was established by the grafting experiments of Hammerling in 1953 with the unicellular algae Acetabularia.
In general, there is only its own nucleus in each cell, but this may vary in different types of cells. Some with more than one nucleus are binucleate like in paramecium while some with many nuclei are multinucleate like in Ascaris. However, some cells lack nucleus known as anucleate at maturity such as mammalian RBCs and sieve tube cells. A typical interphase nucleus is 5-25 mm in diameter.
The outer layer of nucleus is covered with ribosomes and continuous with the endoplasmic reticulum while the inner layer contains lamins that form a structure called nuclear membrane and give structural support to the nucleus. Between these two layers is a perinuclear space about 20 nm. From the above discussion it is clear to all of us that ‘nucleus’ controls most of the activities of the cell.

Note-
It will be interesting to know for you all that the nucleus was the first organelle to be discovered by the scientist.
Nucleus is the largest among the organelle and uses around 10 percent of the cells volume.
As the nucleus controls most of the activities of cells and also contains genetic material, it is known as the command center of cells.