Scientists classify plants using a system called taxonomy, which involves grouping organisms based on their shared characteristics. This system is hierarchical, meaning that organisms are grouped into increasingly specific categories. Here's a breakdown of the main levels of plant classification:

1. Domain: All living things are first classified into three domains:

* Bacteria: Single-celled organisms without a nucleus.

* Archaea: Single-celled organisms without a nucleus, but with distinct biochemical characteristics from bacteria.

* Eukarya: Organisms with cells that have a nucleus and other membrane-bound organelles. Plants belong to this domain.

2. Kingdom: Within the Eukarya domain, plants belong to the Kingdom Plantae.

3. Phylum: Plants are further divided into several phyla based on their evolutionary relationships and key characteristics. Here are some major phyla:

* Bryophyta: Mosses, liverworts, and hornworts - non-vascular plants.

* Pteridophyta: Ferns and their allies - vascular plants with spores.

* Coniferophyta: Conifers like pines, firs, and spruces - vascular plants with cones.

* Magnoliophyta: Flowering plants - vascular plants with flowers and fruits.

4. Class: Within each phylum, plants are grouped into classes based on shared features. For example, the class Magnoliopsida includes dicotyledonous flowering plants (those with two cotyledons in their seeds).

5. Order: Orders group plants based on more specific characteristics than classes. For example, the order Rosales includes plants like roses, apples, and strawberries.

6. Family: Families are groups of plants with even more shared features, such as the Asteraceae family, which includes sunflowers, daisies, and dandelions.

7. Genus: This level groups closely related species together. For example, the genus Rosa includes all the different species of roses.

8. Species: The most specific level of classification, a species is a group of organisms that can interbreed and produce fertile offspring. For example, the Rosa rugosa species is the rugosa rose.

Tools Used in Plant Classification:

* Morphological Features: Observing physical characteristics like leaf shape, flower structure, and seed type.

* Molecular Data: Analyzing DNA and RNA sequences to understand evolutionary relationships.

* Fossil Record: Examining ancient plant remains to trace evolutionary lineages.

* Geographic Distribution: Considering where plants are found and how that influences their characteristics.

Note: Plant classification is constantly being refined as new data emerges. The Linnaean system, with its hierarchical categories, remains a fundamental tool for understanding plant diversity.