diff --git a/README.md b/README.md
index 00a3981..1835ab8 100644
--- a/README.md
+++ b/README.md
@@ -15,6 +15,8 @@
 
 ## Functions
 
+For more extensive examples, please refer to the tests.
+
 ### align(obj: Object, ref: Object)
 
 Align the ordering of one object recursively to a reference object.
@@ -33,6 +35,18 @@ align(obj, ref);
 
 ### contain(tree: Object, subtree: Object)
 
+Check if `subtree` is contained in `tree` recursively.
+
+Different types are never considered _contained_.
+
+Arrays are _contained_ iff they are the same length and every
+element is _contained_ in the corresponding element.
+
+Objects are _contained_ if the keys are a subset,
+and the respective values are _contained_.
+
+All other types are contained if they match exactly (`===`).
+
 _Example:_
 <!-- eslint-disable import/no-unresolved -->
 ```js
@@ -44,3 +58,29 @@ contain({ a: [1, 2], b: 'c' }, { a: [1, 2] });
 contain({ a: [1, 2], b: 'c' }, { a: [1] });
 // => false
 ```
+
+### Merge(logic: Object = {})(...obj: Object[])
+
+Allows merging of objects. The logic defines paths that map to a field, or a function, to merge by.
+
+If a function is passed, it is invoked with the value, and the result is used as the merge identifier.
+
+The paths are defined using [object-scan](https://github.com/blackflux/object-scan) syntax.
+
+_Example:_
+<!-- eslint-disable import/no-unresolved -->
+```js
+const { Merge } = require('object-lig');
+
+Merge()(
+  { children: [{ id: 1 }, { id: 2 }] },
+  { children: [{ id: 2 }, { id: 3 }] }
+);
+// => { children: [ { id: 1 }, { id: 2 }, { id: 2 }, { id: 3 } ] }
+
+Merge({ '**[*]': 'id' })(
+  { children: [{ id: 1 }, { id: 2 }] },
+  { children: [{ id: 2 }, { id: 3 }] }
+);
+// => { children: [ { id: 1 }, { id: 2 }, { id: 3 } ] }
+```
diff --git a/package.json b/package.json
index 918f93c..4321b99 100644
--- a/package.json
+++ b/package.json
@@ -25,6 +25,7 @@
     "eslint-plugin-markdown": "1.0.2",
     "eslint-plugin-mocha": "8.0.0",
     "js-gardener": "2.0.184",
+    "node-tdd": "2.19.1",
     "nyc": "15.1.0",
     "semantic-release": "17.3.7"
   },
@@ -105,5 +106,8 @@
   },
   "engines": {
     "node": ">= 10"
+  },
+  "dependencies": {
+    "object-scan": "13.8.0"
   }
 }
diff --git a/src/core/merge.js b/src/core/merge.js
new file mode 100644
index 0000000..9e51ed2
--- /dev/null
+++ b/src/core/merge.js
@@ -0,0 +1,67 @@
+const objectScan = require('object-scan');
+
+module.exports = (logic_ = {}) => {
+  const logic = { '**': null, ...logic_ };
+  const last = (arr) => arr[arr.length - 1];
+  const mkChild = (ref) => {
+    if (!(ref instanceof Object)) {
+      return ref;
+    }
+    return Array.isArray(ref) ? [] : {};
+  };
+  const populate = (obj, key, fn, force = false) => {
+    if (force === true || !(key in obj)) {
+      // eslint-disable-next-line no-param-reassign
+      obj[key] = fn();
+      return true;
+    }
+    return false;
+  };
+
+  const scanner = objectScan(Object.keys(logic), {
+    reverse: false,
+    breakFn: ({
+      isMatch, property, value, matchedBy, context
+    }) => {
+      if (!isMatch) return;
+      const { stack, groups, path } = context;
+      const current = last(stack);
+      const bestNeedle = last(matchedBy);
+      const groupBy = typeof logic[bestNeedle] === 'function'
+        ? logic[bestNeedle](value)
+        : logic[bestNeedle];
+
+      if (!Array.isArray(current) || groupBy === null) {
+        if (Array.isArray(current)) {
+          current.push(mkChild(value));
+          stack.push(last(current));
+        } else {
+          populate(current, property, () => mkChild(value), !(value instanceof Object));
+          stack.push(current[property]);
+        }
+      } else {
+        const groupId = `${bestNeedle}.${groupBy}: ${path.join('.')}`;
+        populate(groups, groupId, () => ({}));
+        const groupEntryId = value[groupBy];
+        if (populate(groups[groupId], groupEntryId, () => mkChild(value))) {
+          current.push(groups[groupId][groupEntryId]);
+        }
+        path.push(`${groupBy}=${groupEntryId}`);
+        stack.push(groups[groupId][groupEntryId]);
+      }
+    },
+    filterFn: ({ matchedBy, context }) => {
+      const { stack, path } = context;
+      stack.pop();
+      if (logic[last(matchedBy)] !== null) {
+        path.pop();
+      }
+    }
+  });
+  return (...args) => {
+    const result = mkChild(args[0]);
+    const groups = {};
+    args.forEach((arg) => scanner(arg, { stack: [result], groups, path: [] }));
+    return result;
+  };
+};
diff --git a/src/index.js b/src/index.js
index e168254..3e7a302 100644
--- a/src/index.js
+++ b/src/index.js
@@ -1,7 +1,9 @@
 const align = require('./core/align');
 const contain = require('./core/contain');
+const Merge = require('./core/merge');
 
 module.exports = {
   align,
-  contain
+  contain,
+  Merge
 };
diff --git a/test/core/merge.spec.js b/test/core/merge.spec.js
new file mode 100644
index 0000000..3c09b26
--- /dev/null
+++ b/test/core/merge.spec.js
@@ -0,0 +1,39 @@
+const expect = require('chai').expect;
+const { describe } = require('node-tdd');
+const Merge = require('../../src/core/merge');
+
+describe('Testing Merge', () => {
+  it('Testing SO question: https://stackoverflow.com/questions/65822248', ({ fixture }) => {
+    const json1 = fixture('json1');
+    const json2 = fixture('json2');
+    const merge = Merge({
+      '[*]': 'id',
+      '[*].addresses[*]': 'type'
+    });
+    expect(merge(json1, json2)).to.deep.equal(fixture('result'));
+  });
+
+  it('Testing array concat', () => {
+    const d1 = [{ a: 1 }];
+    const d2 = [{ a: 2 }];
+    expect(Merge()(d1, d2)).to.deep.equal([{ a: 1 }, { a: 2 }]);
+  });
+
+  it('Testing array merge', () => {
+    const d1 = [{ a: 1, b: 1, c: 3 }];
+    const d2 = [{ a: 1, b: 2, d: 4 }];
+    expect(Merge({ '[*]': 'a' })(d1, d2)).to.deep.equal([{ ...d1[0], ...d2[0] }]);
+  });
+
+  it('Testing merge by sum', () => {
+    const d1 = [[1, 2, 3], [2, 4], [1, 2]];
+    const d2 = [[3, 3], [1, 5], [3, 2]];
+    expect(Merge({
+      '[*]': (o) => o.reduce((a, b) => a + b, 0)
+    })(d1, d2)).to.deep.equal([
+      [1, 2, 3, 2, 4, 3, 3, 1, 5],
+      [1, 2],
+      [3, 2]
+    ]);
+  });
+});
diff --git a/test/core/merge.spec.js__fixtures/json1.json b/test/core/merge.spec.js__fixtures/json1.json
new file mode 100644
index 0000000..c9f5e06
--- /dev/null
+++ b/test/core/merge.spec.js__fixtures/json1.json
@@ -0,0 +1,30 @@
+[
+  {
+    "id": 1,
+    "name": "aaa",
+    "addresses": [
+      {
+        "type": "office",
+        "city": "office city"
+      },
+      {
+        "type": "home1",
+        "city": "home1 city"
+      }
+    ]
+  },
+  {
+    "id": 2,
+    "name": "bbb",
+    "addresses": [
+      {
+        "type": "office",
+        "city": "office city"
+      },
+      {
+        "type": "home1",
+        "city": "home1 city"
+      }
+    ]
+  }
+]
diff --git a/test/core/merge.spec.js__fixtures/json2.json b/test/core/merge.spec.js__fixtures/json2.json
new file mode 100644
index 0000000..a82a56a
--- /dev/null
+++ b/test/core/merge.spec.js__fixtures/json2.json
@@ -0,0 +1,30 @@
+[
+  {
+    "id": 1,
+    "name": "aaa1",
+    "addresses": [
+      {
+        "type": "home1",
+        "city": "home1 new city"
+      },
+      {
+        "type": "home2",
+        "city": "home2 city"
+      }
+    ]
+  },
+  {
+    "id": 3,
+    "name": "ccc",
+    "addresses": [
+      {
+        "type": "home1",
+        "city": "home1 city"
+      },
+      {
+        "type": "home2",
+        "city": "home2 city"
+      }
+    ]
+  }
+]
diff --git a/test/core/merge.spec.js__fixtures/result.json b/test/core/merge.spec.js__fixtures/result.json
new file mode 100644
index 0000000..057a7a0
--- /dev/null
+++ b/test/core/merge.spec.js__fixtures/result.json
@@ -0,0 +1,48 @@
+[
+  {
+    "id": 1,
+    "name": "aaa1",
+    "addresses": [
+      {
+        "type": "office",
+        "city": "office city"
+      },
+      {
+        "type": "home1",
+        "city": "home1 new city"
+      },
+      {
+        "type": "home2",
+        "city": "home2 city"
+      }
+    ]
+  },
+  {
+    "id": 2,
+    "name": "bbb",
+    "addresses": [
+      {
+        "type": "office",
+        "city": "office city"
+      },
+      {
+        "type": "home1",
+        "city": "home1 city"
+      }
+    ]
+  },
+  {
+    "id": 3,
+    "name": "ccc",
+    "addresses": [
+      {
+        "type": "home1",
+        "city": "home1 city"
+      },
+      {
+        "type": "home2",
+        "city": "home2 city"
+      }
+    ]
+  }
+]
diff --git a/test/index.spec.js b/test/index.spec.js
index 8584847..5926fb6 100644
--- a/test/index.spec.js
+++ b/test/index.spec.js
@@ -5,7 +5,8 @@ describe('Testing index.js', () => {
   it('Testing exported', () => {
     expect(Object.keys(index)).to.deep.equal([
       'align',
-      'contain'
+      'contain',
+      'Merge'
     ]);
   });
 });
diff --git a/yarn.lock b/yarn.lock
index ed42402..8a50184 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1281,7 +1281,7 @@ callsite@^1.0.0:
   resolved "https://registry.yarnpkg.com/callsite/-/callsite-1.0.0.tgz#280398e5d664bd74038b6f0905153e6e8af1bc20"
   integrity sha1-KAOY5dZkvXQDi28JBRU+borxvCA=
 
-callsites@^3.0.0:
+callsites@3.1.0, callsites@^3.0.0:
   version "3.1.0"
   resolved "https://registry.yarnpkg.com/callsites/-/callsites-3.1.0.tgz#b3630abd8943432f54b3f0519238e33cd7df2f73"
   integrity sha512-P8BjAsXvZS+VIDUI11hHCQEv74YT67YUi5JJFNWIqL235sBmjX4+qx9Muvls5ivyNENctx46xQLQ3aTuE7ssaQ==
@@ -4495,7 +4495,7 @@ lodash.mergewith@4.6.2:
   resolved "https://registry.yarnpkg.com/lodash.mergewith/-/lodash.mergewith-4.6.2.tgz#617121f89ac55f59047c7aec1ccd6654c6590f55"
   integrity sha512-GK3g5RPZWTRSeLSpgP8Xhra+pnjBC56q9FZYe1d5RN3TJ35dbkGy3YqBSMbyCrlbi+CM9Z3Jk5yTL7RCsqboyQ==
 
-lodash.set@4.3.2:
+lodash.set@4.3.2, lodash.set@^4.3.2:
   version "4.3.2"
   resolved "https://registry.yarnpkg.com/lodash.set/-/lodash.set-4.3.2.tgz#d8757b1da807dde24816b0d6a84bea1a76230b23"
   integrity sha1-2HV7HagH3eJIFrDWqEvqGnYjCyM=
@@ -4790,7 +4790,7 @@ minimist-options@4.1.0:
     is-plain-obj "^1.1.0"
     kind-of "^6.0.3"
 
-minimist@^1.1.3, minimist@^1.2.0, minimist@^1.2.5:
+minimist@1.2.5, minimist@^1.1.3, minimist@^1.2.0, minimist@^1.2.5:
   version "1.2.5"
   resolved "https://registry.yarnpkg.com/minimist/-/minimist-1.2.5.tgz#67d66014b66a6a8aaa0c083c5fd58df4e4e97602"
   integrity sha512-FM9nNUYrRBAELZQT3xeZQ7fmMOBg6nWNmJKTcgsJeaLstP/UODVpGsr5OhXhhXg6f+qtJ8uiZ+PUxkDWcgIXLw==
@@ -4956,6 +4956,16 @@ nerf-dart@^1.0.0:
   resolved "https://registry.yarnpkg.com/nerf-dart/-/nerf-dart-1.0.0.tgz#e6dab7febf5ad816ea81cf5c629c5a0ebde72c1a"
   integrity sha1-5tq3/r9a2Bbqgc9cYpxaDr3nLBo=
 
+nock@13.0.5:
+  version "13.0.5"
+  resolved "https://registry.yarnpkg.com/nock/-/nock-13.0.5.tgz#a618c6f86372cb79fac04ca9a2d1e4baccdb2414"
+  integrity sha512-1ILZl0zfFm2G4TIeJFW0iHknxr2NyA+aGCMTjDVUsBY4CkMRispF1pfIYkTRdAR/3Bg+UzdEuK0B6HczMQZcCg==
+  dependencies:
+    debug "^4.1.0"
+    json-stringify-safe "^5.0.1"
+    lodash.set "^4.3.2"
+    propagate "^2.0.0"
+
 node-emoji@^1.0.3, node-emoji@^1.10.0:
   version "1.10.0"
   resolved "https://registry.yarnpkg.com/node-emoji/-/node-emoji-1.10.0.tgz#8886abd25d9c7bb61802a658523d1f8d2a89b2da"
@@ -5013,6 +5023,24 @@ node-sass-tilde-importer@^1.0.2:
   dependencies:
     find-parent-dir "^0.3.0"
 
+node-tdd@2.19.1:
+  version "2.19.1"
+  resolved "https://registry.yarnpkg.com/node-tdd/-/node-tdd-2.19.1.tgz#1b1ff2503ecaae9f39b92a877b6db8e8088be3a0"
+  integrity sha512-fEtIFSyVT4ftAA/P3raH/ZIbH4jpPvuYkiV2rteujYOBVpT+KHu0GMKjuFnoaNqNVffNoEz/cptXZKeWhoLCPA==
+  dependencies:
+    callsites "3.1.0"
+    joi-strict "1.2.9"
+    lodash.clonedeep "4.5.0"
+    lodash.get "4.4.2"
+    minimist "1.2.5"
+    nock "13.0.5"
+    object-scan "13.7.1"
+    smart-fs "1.12.3"
+    timekeeper "2.2.0"
+    tmp "0.2.1"
+    uuid "8.3.0"
+    xml2js "0.4.23"
+
 nopt@^4.0.1, nopt@^4.0.3:
   version "4.0.3"
   resolved "https://registry.yarnpkg.com/nopt/-/nopt-4.0.3.tgz#a375cad9d02fd921278d954c2254d5aa57e15e48"
@@ -5435,6 +5463,11 @@ object-scan@13.7.1:
   resolved "https://registry.yarnpkg.com/object-scan/-/object-scan-13.7.1.tgz#2ce78454ae6a35ea45da7f26f2209f5545613122"
   integrity sha512-akfqDKVs77wfaRhcln8p9IVIjfQ6MdgfsqsstAAgBWHHO9OqWjs74IUUqiGihDStpvgKA3fFUqdLpdD2Oi7YkQ==
 
+object-scan@13.8.0:
+  version "13.8.0"
+  resolved "https://registry.yarnpkg.com/object-scan/-/object-scan-13.8.0.tgz#70ec43620b76fbc580856beb5275ee28321f781c"
+  integrity sha512-ljh4WKzs/TTBML0kl+qfTpu13lSZ0Q41aj5XiJa0ue9FkEdP5fi5/FTHbZgsGBiXo/AeyPRh1XZDOuGQLffC1A==
+
 object-treeify@1.1.31:
   version "1.1.31"
   resolved "https://registry.yarnpkg.com/object-treeify/-/object-treeify-1.1.31.tgz#eb083c8eb25b512c9feea088e72b03aa13032d5e"
@@ -6028,6 +6061,11 @@ promzard@^0.3.0:
   dependencies:
     read "1"
 
+propagate@^2.0.0:
+  version "2.0.1"
+  resolved "https://registry.yarnpkg.com/propagate/-/propagate-2.0.1.tgz#40cdedab18085c792334e64f0ac17256d38f9a45"
+  integrity sha512-vGrhOavPSTz4QVNuBNdcNXePNdNMaO1xj9yBeH1ScQPjk/rhg9sSlCXPhMkFuaNNW/syTvYqsnbIJxMBfRbbag==
+
 proto-list@~1.2.1:
   version "1.2.4"
   resolved "https://registry.yarnpkg.com/proto-list/-/proto-list-1.2.4.tgz#212d5bfe1318306a420f6402b8e26ff39647a849"
@@ -6649,7 +6687,7 @@ safe-regex@^1.1.0:
   resolved "https://registry.yarnpkg.com/safer-buffer/-/safer-buffer-2.1.2.tgz#44fa161b0187b9549dd84bb91802f9bd8385cd6a"
   integrity sha512-YZo3K82SD7Riyi0E1EQPojLz7kpepnSQI9IyPbHHg1XXXevb5dJI7tpyN2ADxGcQbHG7vcyRHk0cbwqcQriUtg==
 
-sax@^1.2.4:
+sax@>=0.6.0, sax@^1.2.4:
   version "1.2.4"
   resolved "https://registry.yarnpkg.com/sax/-/sax-1.2.4.tgz#2816234e2378bddc4e5354fab5caa895df7100d9"
   integrity sha512-NqVDv9TpANUjFm0N8uM5GxL36UgKi9/atZw+x7YFnQ8ckwFGKrl4xX4yWtrey3UJm5nP1kUbnYgLopqWNSRhWw==
@@ -7382,11 +7420,23 @@ timed-out@^4.0.0:
   resolved "https://registry.yarnpkg.com/timed-out/-/timed-out-4.0.1.tgz#f32eacac5a175bea25d7fab565ab3ed8741ef56f"
   integrity sha1-8y6srFoXW+ol1/q1Zas+2HQe9W8=
 
+timekeeper@2.2.0:
+  version "2.2.0"
+  resolved "https://registry.yarnpkg.com/timekeeper/-/timekeeper-2.2.0.tgz#9645731fce9e3280a18614a57a9d1b72af3ca368"
+  integrity sha512-W3AmPTJWZkRwu+iSNxPIsLZ2ByADsOLbbLxe46UJyWj3mlYLlwucKiq+/dPm0l9wTzqoF3/2PH0AGFCebjq23A==
+
 tiny-relative-date@^1.3.0:
   version "1.3.0"
   resolved "https://registry.yarnpkg.com/tiny-relative-date/-/tiny-relative-date-1.3.0.tgz#fa08aad501ed730f31cc043181d995c39a935e07"
   integrity sha512-MOQHpzllWxDCHHaDno30hhLfbouoYlOI8YlMNtvKe1zXbjEVhbcEovQxvZrPvtiYW630GQDoMMarCnjfyfHA+A==
 
+tmp@0.2.1:
+  version "0.2.1"
+  resolved "https://registry.yarnpkg.com/tmp/-/tmp-0.2.1.tgz#8457fc3037dcf4719c251367a1af6500ee1ccf14"
+  integrity sha512-76SUhtfqR2Ijn+xllcI5P1oyannHNHByD80W1q447gU3mp9G9PSpGdWmjUOHRDPiHYacIk66W7ubDTuPF3BEtQ==
+  dependencies:
+    rimraf "^3.0.0"
+
 to-fast-properties@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/to-fast-properties/-/to-fast-properties-2.0.0.tgz#dc5e698cbd079265bc73e0377681a4e4e83f616e"
@@ -7765,6 +7815,11 @@ util-promisify@^2.1.0:
   dependencies:
     object.getownpropertydescriptors "^2.0.3"
 
+uuid@8.3.0:
+  version "8.3.0"
+  resolved "https://registry.yarnpkg.com/uuid/-/uuid-8.3.0.tgz#ab738085ca22dc9a8c92725e459b1d507df5d6ea"
+  integrity sha512-fX6Z5o4m6XsXBdli9g7DtWgAx+osMsRRZFKma1mIUsLCz6vRvv+pz5VNbyu9UEDzpMWulZfvpgb/cmDXVulYFQ==
+
 uuid@^3.3.2, uuid@^3.3.3:
   version "3.4.0"
   resolved "https://registry.yarnpkg.com/uuid/-/uuid-3.4.0.tgz#b23e4358afa8a202fe7a100af1f5f883f02007ee"
@@ -8011,6 +8066,19 @@ xml-js@1.6.11:
   dependencies:
     sax "^1.2.4"
 
+xml2js@0.4.23:
+  version "0.4.23"
+  resolved "https://registry.yarnpkg.com/xml2js/-/xml2js-0.4.23.tgz#a0c69516752421eb2ac758ee4d4ccf58843eac66"
+  integrity sha512-ySPiMjM0+pLDftHgXY4By0uswI3SPKLDw/i3UXbnO8M/p28zqexCUoPmQFrYD+/1BzhGJSs2i1ERWKJAtiLrug==
+  dependencies:
+    sax ">=0.6.0"
+    xmlbuilder "~11.0.0"
+
+xmlbuilder@~11.0.0:
+  version "11.0.1"
+  resolved "https://registry.yarnpkg.com/xmlbuilder/-/xmlbuilder-11.0.1.tgz#be9bae1c8a046e76b31127726347d0ad7002beb3"
+  integrity sha512-fDlsI/kFEx7gLvbecc0/ohLG50fugQp8ryHzMTuW9vSa1GJ0XYWKnhsUx7oie3G98+r56aTQIUB4kht42R3JvA==
+
 xtend@^4.0.0, xtend@^4.0.1, xtend@~4.0.1:
   version "4.0.2"
   resolved "https://registry.yarnpkg.com/xtend/-/xtend-4.0.2.tgz#bb72779f5fa465186b1f438f674fa347fdb5db54"