A hen's egg can be seen easily. Is it a cell or group of cells?
Hint: Hen's egg can be seen easily before fertilisation and these eggs have different numbers of cells before and after fertilisation.
Complete answer: A Hen's egg is a single cell just like the ostrich egg which is really big in size. But it becomes multicellular after it hatches to form a chick then the chick will have a group of cells. Before the fertilisation or you can say when the egg is unfertilised then the egg contains a single celled haploid ovum. After fertilisation or you can say when the egg is fertilised i.e., when there is fusion of ovum with sperm cell then it contains a single celled diploid zygote. Now this diploid zygote will grow into an embryo, along with this single cell gets divided into multiple times. Therefore, an embryo is multicellular. The yolk content contains all the necessary nutrients when the egg is laid which is required for the growth of the baby if the egg is fertilised.
Thus, hen's egg is a single cell structure before the fertilisation which can be seen by naked eyes.
Additional Information: There are thousands of tiny ova in chickens which are undeveloped in their ovary but when they have matured ones then an ovum will be released into the oviduct and journey of development will start there. A hen can have many eggs at different stages of development at one time within her reproductive system.
Note: Before fertilisation, hen's egg is a single cell inside the shell but after fertilisation the cells get fused and then it gets divided into two cells i.e., diploid zygote inside the shell. Therefore, before fertilisation it can be seen by naked eyes.