During leptotene stage of prophase-$1$in meiosis $I$, the chromosomes become gradually visible under the light microscope. The compaction of chromosomes continues throughout leptotene.
The sequence of growth and division of a cell, and consists of a series of biological processes, particularly the resting phase (G0), the interphase (G1, S, G2), and cell division (i.e. mitosis and cytokinesis)