Fastidious is an Adjective.
i) Being extremely particular or critical about the smallest detail, meticulous, having very high standards and difficult to please, highly sensitive to faults, a perfectionist
ii) With reference to Biology, it is used to describe organisms which grow in a particular medium and under specific conditions and nutritional needs like hydrophytic and xerophytic organisms.
1. Actor Amir Khan's fastidious approach towards films has earned him a lot of success.
2. The new restaurant in the neighborhood caters to elite and fastidious customers who appreciate finer things in life.
3. Mrs.Gupta is so fastidious about reducing her weight that she does not eat anything before counting its calories.