Who came first prokaryotes or eukaryotes?

Hint: On the basis of organization of genetic material, the cells are of two types – prokaryotic cells and eukaryotic cells. The prokaryotic cells are represented by the bacteria, cyanobacteria or Blue Green Algae (BGA), mycoplasma or PPLOs, spirochaete and rickettsiae.
Eukaryotic cells have a true nucleus, which contains DNA enclosed by a double membrane envelope. They occur in some protists, fungi, plants and animals.

Complete Answer-
The word ‘prokaryote’ is made up of ‘pro’ meaning old and ‘karyone’ meaning cells. These cells are usually small in size. The word ‘eukaryote’ is made up of two words ‘eu’ means advance and ‘karyone’ means cells.
Prokaryotes are underdeveloped cells, undifferentiated organelles with no nuclei. They have circular DNA. It suggests that prokaryotes evolved first while eukaryotes have well defined membrane bound nucleus and cell organelles.
The first organisms to evolve on earth were bacteria. They come under the category of prokaryotic heterotroph. Due to absence of oxygen at that time, these first bacteria were anaerobic and also heterotrophic due to lack of photosynthesis process. Similarly, the first photosynthetic bacteria to evolve on earth were cyanobacteria. They appeared about 2.5 billion years ago. Primitive bacteria later led to evolution of eukaryotic organisms about 2 billion years ago.

Note-
After the emergence of both prokaryotic or eukaryotic organisms, the conditions slowly continued to become favorable which started resulting in gradual evolution of different complex life forms.
Cyanobacteria started making their own food by using water and sunlight. It brought an unremarkable change in the atmosphere of the earth by releasing oxygen and also it helps in the smooth liveliness of aerobic organisms.