Living things grow and develop in a number of differing ways depending on their biological and chemical make-up, and the type of organism they are.
We tend to think of "living things" as humans, plants and animals, but in reality these are just types of complex living things. Anything which has cells- even a single cell organism like an amoebae, algae or certain types of parasites- are considered to be living.
We know that humans and animals need food and water to develop and grow, and plants require water and nutrients from the soil and sunlight to perform photosynthesis. All of these things contribute to cell growth and division and the replication of DNA which leads to an increase in size and to the development of structures that make up the living thing.