Healthcare Why do we need sleep? Scientists answer the age old question Updated : September 24, 2020 12:06 AM IST Since birth, until two-and-half years, the brain is in development mode and it grows rapidly. During this stage, it is advised not to wake a child up as the brain undergoes massive developmental changes. Subscribe to Moneycontrol PRO at just Rs.33/- per month for the first year. Use code SUPERPRO. Limited period offer. Available on Web and Android.