"gradually develop into" is a correct and usable phrase in written English.
It means to progress or evolve over time into something. This phrase can be used when describing a gradual transformation or change that occurs over a period of time. Example: The small startup company gradually developed into a multinational corporation over the course of 10 years.
Without periodic burning, many scrublands would alter in composition; some would gradually develop into tree-dominated vegetation.
The pianist Pierre-Laurent Aimard, one of the orchestra's five artistic partners, as it calls them, conducted Karlheinz Stockhausen's "Kontra-Punkte," a work that begins with points of musical color that gradually develop into contrapuntal lines, which in turn dissipate as one player after another drops out while seemingly remaining at the ready.
As the decrease in temperature and injection pressure of the second melt, the number of cylindritic structures in the core layer decreases and the cylindritic structures gradually develop into irregularly-arranged spherulites.
Many of the help-at-home programs have received funding from the EU in the past, in the hope that they would gradually develop into permanent services.
During middle years, children gradually develop into more independent and separate human beings who are capable of exploring the world around them.
Approximately 1 h after the completion of inversion, the cell shapes change for the last time: all the column-shaped cells gradually develop into what we refer to as gemstone-shaped cells.
It gradually developed into a vibrant democracy.
The idea gradually developed into a consensus over many years.
In 1910 he went to Paris fell under Cubist influence and gradually developed into an abstractionist.
We had great conversations, but it really gradually developed into a romantic relationship.
Dancers arranged themselves in circles, or sometimes lines, which gradually developed into chain dances.
